BTI10202/BTI1022 DTI2143

1. UTHM Sem I 2010/11
Lecture Notes
Computer Programming
BTI 1022
Lecturer:
Winardi Sani, Dipl.-Ing.
Tutors:
Imran bin Razali
Muhamad Zaini bin Yunos
Sharifah Z.R. Bt Syed Ahmad
Faizul Amin Anuar
Faculty of Mechanical Engineering
Universiti Tun Hussein Onn Malaysia

3. Table of Content
1 Introduction 1-1
1.1 Lesson Plan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1
1.2 Computer system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1
1.3 Computer programming . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2
1.4 Software development method . . . . . . . . . . . . . . . . . . . . . . 1-2
1.5 Algorithm and Pseudo code . . . . . . . . . . . . . . . . . . . . . . . . 1-3
1.6 Flow chart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5
2 Structure of C Programs 2-1
2.1 Program Development . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1
2.2 Compiler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1
2.3 Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2
2.4 Structures of a C Program . . . . . . . . . . . . . . . . . . . . . . . . . . 2-3
2.5 Identifiers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-3
2.6 Data types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-4
2.6.1 Basic data types . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-4
2.6.1.1 Qualifiers . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-4
2.7 Variables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-5
2.7.1 Variable definition . . . . . . . . . . . . . . . . . . . . . . . . . . 2-5
2.8 Constants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-6
2.8.1 Integer constants . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-6
2.8.2 Floating point constants . . . . . . . . . . . . . . . . . . . . . . . 2-6
2.8.3 Character constants . . . . . . . . . . . . . . . . . . . . . . . . . 2-7
2.8.4 String constants . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-7
2.8.5 Defined constants . . . . . . . . . . . . . . . . . . . . . . . . . . 2-8
2.8.6 Memory constants . . . . . . . . . . . . . . . . . . . . . . . . . . 2-8
2.8.7 A program example . . . . . . . . . . . . . . . . . . . . . . . . . 2-8
2.9 Formatted Input/Output . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-9
2.9.1 printf() . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-9
2.9.2 Output examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-11
2.10 Formatted input . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-11
2.10.1 Input examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-12
2.11 Self exercises . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-12
2.12 Keywords . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-13
2.13 ASCII Code Table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-14
3 Operators and Expressions 3-1
3.1 Arithmetic Operators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1
3.1.1 Integer Arithmetic . . . . . . . . . . . . . . . . . . . . . . . . . . 3-2
3

4. Table of Content
3.1.2 Floating point arithmetic . . . . . . . . . . . . . . . . . . . . . . 3-3
3.1.3 Mixed mode arithmetic . . . . . . . . . . . . . . . . . . . . . . . 3-3
3.2 Relational and Logical Operators . . . . . . . . . . . . . . . . . . . . . 3-3
3.2.1 Relational Operators . . . . . . . . . . . . . . . . . . . . . . . . . 3-3
3.2.2 Logical Operators . . . . . . . . . . . . . . . . . . . . . . . . . . 3-4
3.3 Assignment Operators . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-6
3.3.1 Simple Assignment . . . . . . . . . . . . . . . . . . . . . . . . . . 3-6
3.3.2 Compound Assignment . . . . . . . . . . . . . . . . . . . . . . . 3-6
3.4 Increment and Decrement Operators . . . . . . . . . . . . . . . . . . 3-7
3.4.1 Side Effects of the Increment and Decrement Operators . . . 3-7
3.5 Bit Operators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-8
3.5.1 Bit-Shift Operators . . . . . . . . . . . . . . . . . . . . . . . . . . 3-8
3.5.2 Bit Logical Operators . . . . . . . . . . . . . . . . . . . . . . . . . 3-9
3.6 Cast Operator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-10
3.6.1 Casting Floating-Point Values to Integers . . . . . . . . . . . . . 3-11
3.7 Operator Precedence . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-11
3.8 Exercises . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-13
4 Selections 4-1
4.1 Statements and Block . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1
4.2 if statement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1
4.3 if - else statement . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-2
4.4 switch statement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-4
4.4.1 Evaluation of switch statement . . . . . . . . . . . . . . . . . . 4-4
4.5 else - if statement . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-6
4.6 Conditional Expressions . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-7
4.7 Exercises . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-8
5 Repetition 5-1
5.1 Concept of a loop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-1
5.2 Pretest and Post–Test Loop . . . . . . . . . . . . . . . . . . . . . . . . . 5-1
5.3 Loops in C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-3
5.4 while Loop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-3
5.5 do..while Loop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-5
5.6 for Loop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-6
5.7 continue Statement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-9
5.8 Exercises . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-10
6 Functions 6-1
6.1 Top-Down Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-1
6.2 Functions in C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-1
6.2.1 Advantages of Functions . . . . . . . . . . . . . . . . . . . . . . 6-2
6.3 User-Defined Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-2
4

5. Table of Content
6.4 Recursive . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-6
6.5 Parameter Passing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-7
6.5.1 Pass by Value . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-7
6.5.2 Pass by Address . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-8
6.6 Math Library . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-9
6.7 Exercises . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-10
5

7. CHAPTER 1
Introduction
1.1 Lesson Plan
Delivery Methods
• Lecture: 1 hour.
• Lab. Work (CAD/CAE Lab): 3 hours.
Assessment Scheme
Type of Assessments Weight Where to do
Test 1 and Test 2 30% On computer
Assignments and Group Project 30%
Final Examination 40% Examination Hall
Ran cangan Pengajaran dan Pembelajaran
1.2 Computer system
What is computer?
A computer is an automatic device that performs calculations, makes decisions,
and has capacity for storing and processing vast amounts of data. A computer
has two main parts: hardware and software
Computer Hardware
Hardware is the electronic and mechanical parts of the computer including:
• Input device: Keyboard, Mouse, Scanner, Touch screener, Pen or stylus
• Central Processing Unit (CPU). It executes instructions (arithmetic opera-
tions)
• Primary storage or main memory: RAM
• Secondary storage: HD, FD, CD,DVD
• Output device:Monitor, Printer, Plotter, Speaker
Computer Software
Two categories: System software and Application software
• System software: it manages the H/W resources and performs processing
tasks. Three classes :
1-1

8. 1 Introduction
1. Operating system: it provides services such as a user interface, files and
database access and communication systems.
2. System support software: System utilities such as disk format.
3. System development softwares: Interpreters/compilers that convert pro-
grams into machine language. Assembler, C, C++, Basic, Java, etc.
• Application software: word processors, DB management systems, CAD/-
CAE.
1.3 Computer programming
To write a program for a computer, we must use a computer language or a pro-
gramming language.
• Machine language: Each computer has its own machine language consist-
ing of 0s and 1s program. Not readable for human being.
• Symbolic language:
– Low-level language/Assembly language: Assembler
– High-level language/Compiler: Fortran, Pascal, C, C++
• Natural language: in development phase
Computer programming (often shortened to programming or coding) is the
process of designing, writing, testing, debugging / troubleshooting, and main-
taining the source code of computer programs. This source code is written in a
programming language.
1.4 Software development method
• Specify problem
• Analyze problem
• Design algorithm
• Implement algorithm (write a C program)
• Test and verify program
• Maintain and update program
Algorithm
A set of instructions for solving a problem, or, an ordered sequence of unambigu-
ous and well-defined instructions that performs some task and halts in finite time
(Al Kho-war-iz-mi a 9th century Persian mathematician).
Algorithm
Three Catagories of Algorithmic Operations
1-2

9. 1.5 Algorithm and Pseudo code
• sequential operations - instructions are executed in order
• conditional (”question asking”) operations - a control structure that asks a
true/false question and then selects the next instruction based on the an-
swer
• iterative operations (loops) - a control structure that repeats the execution
of a block of instructions
How to represent algorithms?
• Use natural languages: too verbose
• Use formal programming languages: too low level, complicated syntax of
programming language
• Pseudo-Code: natural language constructs modeled to look like statements
available in many programming languages
• Flow chart: a common type of diagram, that represents an algorithm or
process, showing the steps as boxes of various kinds, and their order by con-
necting these with arrows
1.5 Algorithm and Pseudo code
Pseudo code
Pseudo-Code is simply a numbered list of instructions to perform some task. Pseudo-
code is best understood by looking at examples.
Example 1
Computing Sales Tax : Pseudo-code the task of computing the final price of an
item after figuring in sales tax. Note the three types of instructions: input (get or
read), process/calculate (=) and output (display)
1. start
2. get price of item
3. get sales tax rate
4. sales tax = price of item * sales tax rate
5. final price = price of item + sales tax
6. display final price
7. halt/end
1-3

10. 1 Introduction
Example 2
Computing Weekly Wages: Gross pay depends on the pay rate and the number
of hours worked per week. However, if you work more than 40 hours, you get paid
time-and-a-half for all hours worked over 40. Pseudo-code the task of computing
gross pay given pay rate and hours worked.
1. start
2. get hours worked
3. if hours worked ≤ 40 then
a) gross pay = pay rate * hours worked
4. else
a) gross pay = pay rate * 40 + 1.5 * pay rate *(hours worked - 40)
5. display gross pay
6. halt/end
Example 3
Computing a Quiz Average: Pseudo-code a routine to calculate your quiz aver-
age.
1. start
2. get number of quizzes
3. sum = 0
4. count = 0
5. while count < number of quizzes
a) get quiz grade
b) sum = sum + quiz grade
c) count = count + 1
6. average = sum / number of quizzes
7. display average
8. halt/end
Pseudo code construction
Computation/Assignments
"variable" = "expression"
1-4

11. 1.6 Flow chart
Input/Output
get "variable", "variable", ...
display "variable", "variable",
Condition
if "condition"
statement
Iterative
while "condition"
statement
Rules for a pseudo code construction
1. Consist of a statement of instructions in sequence
2. Every step consists of keyword
3. Every step should be written in different step, if continued, thr next row must
be indented
4. if/else for condition, while/do for repetition
5. Every step must contain clear statement and easy to understand
6. Use start for beginning of operation, and end/halt for finishing it.
Exercise
A box has a dimension in height, width, and length. Write a pseudo code to
calculate the volume of the box.
More exercise in the lab work.
1.6 Flow chart
Flow chart
flow chart gives the logical flow of the solution in a diagrammatic form, and pro-
vides a plan from which the computer program can be written. The logical flow
of an algorithm can be seen by tracing through the flowchart. Some standard
symbols:
1-5

12. 1 Introduction
Flowchart constructs
The flowchart equivalents for the structured programming constructs are shown
below:
Selection
Sequence
single (if) double (if-else) multiple (switch-case)
Flowchart constructs,con’t
1-6

13. 1.6 Flow chart
Repetition
while do..while for
Examples of a Flow chart
Example 1 and 2 are solved using a flow chart:
Exercises of algorithm constructions
Self exercises
1. Construct a flowchart for the pseudo-code given in example 3.
2. Express an algorithm to get two numbers from the user ( dividend and divi-
sor), testing to make sure that the divisor member is not zero, and displaying
their quotient using a flowchart and a pseudo-code.
y
z= , x=0
x
3. See the formula below:

 x if x ≥ 0
f (x) =
 −x if x < 0
1-7

14. 1 Introduction
Write a pseudo-code and the relevant algorithm to solve the function.
4. Follow the instruction given by the tutor for more exercises and assignments.
1-8

15. CHAPTER 2
Structure of C Programs
2.1 Program Development
• A programmer writes a source code in an editor.
• The compiler translates it into a machine code (.obj). If any syntax errors
exists, their must be fixed (compiling time).
• Together with other object codes, if any, the linker generates an executable
code.
• During program execution, error may exist (run time), and correction must
be done at this stage (debugging).
• The cycle of modifying the source code, compiling, linking, and running
continues until the program is complete and free of errors.
• Errors occurring at compiling time are normal, especially for learners.
2.2 Compiler
In this course, Turbo C is used as the compiler and it works under MS-DOS. It can
be downloaded in internet for free (hopefully). Turbo C supports an Integrated
Development Environment (IDE) and compiler for the C programming language
from Borland.
2-1

16. 2 Structure of C Programs
2.3 Background
Year Language Remarks
1960 ALGOL(Algorithmic in teaching compiler construction
Language)
1967 BCPL (Basic Combined Compiler writing
Programming Lan-
guage
1970 B System programming (type less)
1972 C Combination of BCPL and B
1978 Standard traditional C Kerninghan and Ritchie
1989 ANSI/ISO C American National Standards Institute
1990 ISO C Standard for C
Features of C:
• very efficient and fast. This is due to its variety of data types and powerful
operators. It is many time faster than BASIC
• a powerful and flexible language which helps system developers to deliver
various complex tasks with ease. C is used for diverse projects as operating
systems, word processors, graphics, spreadsheets, and even compilers for
other languages.
• C is popular among professional programmers for programming. Matlab is
an example.
• C is highly portable language.
• Writing C program with user-defined functions makes program more simple
and easy to understand. Breaking a problem in terms of functions makes
program debugging, maintenance and testing easier.
• its ability to extend itself. A C program is basically a collection of various
function supported by C library (also known as header files). We can also
add our own functions to the C library.
2-2

17. 2.4 Structures of a C Program
2.4 Structures of a C Program
• A C program (source code) must
have a file extention .c
• Every C program must contain min-
imum a main function. A function
may contain local variables and
statements. The purpose of main
function is for program execution.
• return 0 means the resource control
is passed back to the operating sys-
tem.
• Preprocessor directives or precom-
piler directives are necessary for
preparing the system during pro-
gram compilation. Every direc-
tive starts with a hash symbol (#).
include<stdio.h> is the most im-
portant one that inserts a header
file for formating data in the stan-
dard input output devices (key-
board and screen). scanf() and
printf() are defined in this header
file.
• Compiler reads a source code from
top downward and left to right.
2.5 Identifiers
Purposes of an identifier in any programming language:
1. To name data and other objects. Every data in a computer is stored at
a unique address. The identifier is also a symbolic representation of data
location.
2. To allow the compiler keep track of the data using the identifier to locate
where the data is stored inside the computer memory. Rule of an identifier:
2-3

18. 2 Structure of C Programs
a) First character must be alphabetic or underscore.
b) It must consist of alphabetic characters (A . . . Z, a . . . z, digits (0 . . . 9), or
underscore (_).
c) The first 31 characters are significant. C is case-sensitive.
d) It can not duplicate a reserved words (keywords).
Valid identifier Invalid identifier
Name Comment
a $sum $ is illegal
student_name 2name First char is digit
_force int Reserved word
2.6 Data types
A data type defines a set of values and a set of operations that can be applied
on these values. A function has also a data type that returns after its call. Classi-
fication of the data types in C language:
• Basic data type
• Derived data type
• User-defined data type
In this course, the emphasis is on the basic data type.
2.6.1 Basic data types
The size of a data type is machine dependent. It can vary from computer to
computer. The most common sizes of the data sizes on 16 – bit machine are
shown in table 2.1.
2.6.1.1 Qualifiers
To manage the memory allocation for the basic data type, ANSI C provides qual-
ifiers:
• short and long provide a different length for an integer data type. short
is often 16 bits long, and int only either 16 or 32 bits.
2-4

19. 2.7 Variables
Table 2.1: Basic data types
Name Type Size in Bytes (bits) Range of values Declaration
Integer int 2 (16) -32,768 . . . 32,767 int a;
Character char 1 (8) -128 . . . 127 char c;
Floating Point float 4 (32) −2−31 . . . 231 − 1 float f;
Double precision floating Point double 8 (64) −2−63 . . . 263 − 1 double d;
Void void - Generic type void main()
• signed and unsigned may be applied on a character and any integer.
unsigned numbers are always positive or zero.
Qualifier Memory allocation/Size Data range Example
short int 2 Bytes -32,768 . . . 32,767 short int a
long int 4 Bytes −2−31 . . . 231 − 1 long int b
int 2 Bytes -32,768 . . . 32,767 int a;
unsigned int 2 Bytes 0 . . . 65,535 unsigned int a;
unsigned char 1 Byte 0 . . . 255 unsigned char a;
2.7 Variables
A variable is a symbolic name for a certain memory location in a computer ma-
chine. It has a type and consequently a memory size and a set of operations to
manipulate the data.
2.7.1 Variable definition
• Each variable must be first declared and defined before use. Every variable
has a data type for the memory allocation and a set of operations applied
on it.
Defining a variable means creating an object. Examples:
int counter; /* variable definition. */
int sum = 0; /* variable definition with initialization*/
char c = ’c’;
2-5

20. 2 Structure of C Programs
We can initialize a variable at the definition time by an initial value using an
assignment (=) operator.
2.8 Constants
Constants are data values that cannot be changed during the program execu-
tion. Every constant has a data type.
2.8.1 Integer constants
Eventhough integers are stored in the binary form, they are simply coded in dec-
imal form. Types of an integer constant are”
• signed integer, signed long
• unsigned integer, unsigned long
Literal Value Type Example
+123 123 int int sum = +123
-123 -123 int int sum = -123
-12345L 123,45 long int long int sum = -12345L
1234LU 1,234 unsigned long int sum = sum + 1234LU
Omitting the suffix on a literal, it defaults to int. The Suffix L or l is for a long type,
and u or U for the unsigned type.
2.8.2 Floating point constants
Floating point constants are number with decimal parts and stored in memory as
two parts: the significand and the exponent. The default form for float constant
is double. The Suffix F or f is used for a float type, and L or l for long double.
Literal Value Type Example
0. 0.0 double double sum = 0.
.0 0.0 double int sum = .0
-2.0f -2.0 float float sum = sum + -2.0f
3.1415926L 3.1415926 long double sum = sum + 3.1415926L
2-6

21. 2.8 Constants
2.8.3 Character constants
A character constant is enclosed in two single quotes (apostrophes) such as ’y’.
The value of a character constant is the numeric value of the character in the
machine’s character set. For example, in the ASCII (American Standard Codes
for Information Interchange) character set the character constant ’0’ has the
value 48, which is unrelated to the numeric value 0.
Special characters that begin with a backslash () are used for special pur-
posed (escape sequences).
Symbolic name ASCII char. Symbolic name ASCII char.
’0’ null ’a’ alert (bell)
’b’ backspace ’t’ horizontal tab
’n’ newline ’v’ vertical tab
’r’ carriage return ’’ backslash
The program below will show the output of a character constant in different for-
mats.
1 #include <stdio.h> The program will display:
2 void main (){
3 char c;
Char d in ASCII code is a 100.
4 c=’d’; The same character constant will
5 printf (‘‘nChar %c in ASCII code be displayed in different output
6 is a %d n’’,c,c); formats (%c and %d). There are 255
7 }
characters defined in ASCII code.
2.8.4 String constants
A string constant, or string literal, is a sequence of zero or more characters sur-
rounded by double quotes, as in:
’’I am a string’’
The quotes are not part of the string, but serve only to delimit it. Technically, a
string constant is an array of characters. The internal representation of a string
has a null character ’0’ at the end, so the physical storage required is one more
than the number of characters written between the quotes.
Be careful to distinguish between a character constant and a string that con-
tains a single character: ’x’ is not the same as “x”. The former is an integer, used
to produce the numeric value of the letter x in the machine’s character set. The
latter is an array of characters that contains one character (the letter x) and a
’0’.
2-7

22. 2 Structure of C Programs
2.8.5 Defined constants
Another way to designate a constant is to use the preprocessor command define.
Example:
#define SALES_TAX_RATE 0.15
At the compiling time, SALES_TAX_RATE will be replaced by the value 0.15.
There is no semi colon (;) at the end of the preprocessor command. Defined
constants are usually written in capital letters to distinguish with variable names.
2.8.6 Memory constants
A memory constant uses a type qualifier (const) to indicate that tha data can-
not be changed. Example:
const float SALES_TAX_RATE = 0.15;
const double PI = 3.1459;
2.8.7 A program example
The program below calculates the area of the circle with a radius as the input.
1 /* This program calculates the area of a circle
2 with the radius as the input.
3 Author : Name of student
4 Matrix : Student’s Matrix Number
5 Seksyen : S?
6 Date : Date of submission
7 Instructor: Lab instructor/tutor
8 */
9 #include<stdio.h>
10 #define PI 3.14159
11 void main(){
12 const double pi = 3.14159;
13 double rad, area;
14 printf(‘‘nWhat is the radius of the circle: ’’);
15 scanf(‘‘%f’’,&rad);
16 area = PI * rad * rad;
17 printf(‘‘nThe area of the circle is: %fn’’,area);
18 area = pi * rad * rad;
19 printf(‘‘nThe area of the circle is: %fn’’,area);
20 }
2-8

23. 2.9 Formatted Input/Output
2.9 Formatted Input/Output
C uses two different functions to format input and output.
• printf()
this function writes the formatted output on monitor/screen. Monitor is con-
sidered as an output file.
• scanf()
this function red the formatted input from keyboard. Keyboard is defined as
an input file.
To use the functions, you must include a header file stdio.h at the beginning
part of your program, see the program example above.
2.9.1 printf()
printf(format string, data list)
The formatted output printf() requires two parameters:
1. format string
it contains any text data to be printed and instructions for formatting. The
format string is enclosed in a set of double quotation marks (“text and field
specification”). The field specification for formatting purpose has the syntax:
%<flag><minimum width><precision><size>conversion-code
• conversion-code: c for character, d for integer, and f for floating
point.
• Size: it is used to modify the type specified in the conversion code.
There are different sizes:
– h: this size is used with integer to indicate that the variable is short
integer.
– l: this size is used with integer to indicate that the variable is long
integer.
– L: this size is used with floating point number to indicate that the
variable is long double
There is no size for the data types: int, char, and float. Examples:
2-9

24. 2 Structure of C Programs
Size Code Type Example
- c char %c
h d short int %hd
d int %d
l d long int %ld
- f float %f
- f double %f
L f long double %Lf
e float in exponential form. %e
le long double in exponential form. %le
E float in Exponential form. %E
• width: It is used to specify the minimum number of positions in the
output. It is useful to align output in column. For a floating point num-
ber, the number of decimal places can be specified using a precision
modifier with the format:
.m
where m is number of decimal digits. If width and precision are used, the
width must be larger enough to contain the integral value, the decimal
point, and the number of digits. Examples:
%2hd /* short integer, 2 print positions */
%4d /* integer, 4 print positions */
%8ld /* long int, 8 positions */
%7.2f /* float, 7 print positions: nnnn.dd */
%10.3Lf /* long double, 10 positions: nnnnnn.ddd */
• flag: If the flag is zero and there is a width specification, then a num-
ber will be printed with leading zeros. If the flag is a minus sign (-). then
the data is formatted left justified.
%-8d /* decimal, 8 print pos, left-justified */
%08d /* decimal, 8 print pos, leading zeros */
2. data list
The second parameter is the data list to be printed on the monitor with the
format set by the first parameter in the field specification. The data list may
be a constant, variable name, or a combination of them.
2-10

25. 2.10 Formatted input
2.9.2 Output examples
The following examples show the use of printf.
1. printf(‘‘%d%c%f’’,23, ’z’, 4.1)
Display:
23z4.100000
There is no space in the field specification.
2. printf(‘‘%d %c %f’’,23, ’z’, 4.1)
Display:
23 z 4.100000
3. int number1 = 23;
char c = ’z’;
float number2 = 4.1;
printf(‘‘%d %c %f’’,number1, c, number2)
Display:
23 z 4.100000
4. printf(‘‘%dt%ct%5.1fn’’,number1, c, number2)
printf(‘‘%dt%ct%5.1fn’’,107, ’A’, 53.6)
Display:
23 z 4.1
107 A 53.6
5. printf(‘‘’’%8c %d’’’’,’h’,23)
Display:
‘‘ h 23’’
Quotes are printed using escape character ().
2.10 Formatted input
The standard formatted input in C is scanf(). It requires two parameters : format
string and address list. The format string describes the data and the address list
identifies where the data to be placed in memory. The format string in printf()
can also be applied to scanf().
2-11

26. 2 Structure of C Programs
scanf(format string, address list)
To indicate an address you must prefix the variable name with an address op-
erator, the ampersand (&).
The following rules are applied for using scanf():
1. The conversion operation continues until:
• End of file is reached.
• The maximum number of characters have been processed.
• A whitespace character is found after a digit in a numeric application.
• An error is detected.
2. There must be a field specification for each variable to be read.
3. There must be a variable address of the proper type for each field specifi-
cation.
4. Any character in the format string other than whitespace or a field spec-
ification must be exactly matched by the user during the input, otherwise
scanf stops.
2.10.1 Input examples
The following examples show the use of scanf.
1. Input: 214 156 14 z
scanf(‘‘%d %d %d %c’’, &a, &b, &c, &d);
2. Input: 214 156 2.14
scanf(‘‘%d %d %d %f’’, &a, &b, &c);
3. Input: 14/26 15/77
scanf(‘‘%2d/2%d %2d/%2d’’, &a, &b, &c,&d);
4. Input: 20-7-2010
scanf(‘‘%d-%d-%d’’, &a, &b, &c);
2.11 Self exercises
1. Code the variable definitions for each of the following:
a) a character variable named option.
b) an integer variable, sum, initialized to 0.
2-12

27. 2.12 Keywords
c) a floating point variable, product, initialized to 1.
2. Write a C program that calculates the perimeter, the surface area, and
the volume of a cylinder. The input data: the radius and the height of the
cylinder. Use proper data types for each variable, and write on the screen
the value of radius, height, surface area, perimeter, and the volume. The
data output shall be in convenient format.
3. What is the difference between the data type of short, int, and long int,
with respect to:
a) Memory allocation
b) Type format, and
c) The lower and upper data limit?
4. Write a program to verify your answer in question 3 through an addition of
two different integer numbers.
5. To write a constant, C provides two alternatives. You can use a keyword
const or define the constant in the precompiler part using #define. Explain
the difference between them.
2.12 Keywords
The C language contains several keywords or reserved words that cannot be
used for functions, variables, and named constants. They are shown in table 2.2.
Table 2.2: Keywords of C language
auto extern sizeof break case float
static struct char for const goto
switch continue if typedef default int
union do long unsigned double register
void else return volatile enum short
while signed define main
2-13

28. 2 Structure of C Programs
2.13 ASCII Code Table
Figure 2.1: 7-bit ASCII codes table
2-14

29. CHAPTER 3
Operators and Expressions
Operators are symbols which take one or more operands or expressions and per-
form arithmetic or logical computations of data. An expression is a sequence of
operands and operators that reduces to a single value: Example of an expres-
sion:
2 + 7
Plus sign (+) is the operator for addition and 2 and 7 are the operands that
receive an action of the operator for an addition. This expression reduces to a
single value (9). C language has a set of operators including:
1 Arithmetic Operators
2 Relational and Logical Operators
3 Assignment Operators
4 Increments and Decrement Operators
5 Conditional Operators
6 Bit Operators
There is no limit to the number of operator and operand sets that may be com-
bined to form an expression. The only rule is that, when they have been evalu-
ated the result is a single value that represents the expression.
3.1 Arithmetic Operators
All the basic arithmetic operations can be carried out in C. All the operators
have almost the same meaning as in other languages. Both unary and binary
operations are available in C language. Unary operations operate on a singe
operand, therefore the number 5 when operated by unary – will have the value
-5.
3-1

30. 3 Operators and Expressions
3.1.1 Integer Arithmetic
When an arithmetic operation is performed on two whole numbers or integers
than such an operation is called as integer arithmetic. It always gives an integer
as the result. In integer division the fractional part is truncated.
Let x = 27 and y = 5 be 2 two integer numbers. Then the integer operation leads
to the results shown in Table 3.1. The modulus operator (%) is valid only for integer
type.
Table 3.1: Integer Arithmetic Operators
Operator Use for Example Result/Remark
(x = 27, y = 5)
+ Addition x+y 32
- Subtraction x-y 22
* Multiplication x*y 135
/ Division x/y 5
Modulo (Remain-
% der of an integers x%y 2 (2 = 27 − 5 ∗ 5).
division)
Program example:
1 #include<stdio.h>
2 #include<conio.h>
3 /* tell the compiler the start of the program */
4 void main(){
5 /* declaration of variables */
6 int numb1, num2, sum, sub, mul, div, mod;
7 clrsc();/* make screen clear */
8 scanf (‘‘%d %dˇ, &num1, &num2); /*inputs the operands */
T
9
10 sum = num1+num2; /*addition of numbers and storing in sum.*/
11 printf(‘‘n The sum is = %d’’,sum);/*display the output */
12
13 sub = num1-num2; /*subtraction of numbers and storing in sub.*/
3-2

31. 3.2 Relational and Logical Operators
14 printf(‘‘n The difference is = %d’’,sub);/*display the output */
15
16 mul = num1*num2; /*multiplication and storing in mul. */
17 printf(‘‘n The product is = %d’’,mul);/*display the output */
18
19 div = num1/num2; /*division of numbers and storing in div. */
20 printf(‘‘n The division is = %d’’,div);/*display the output */
21
22 mod = num1%num2; /*modulus of numbers and storing in mod. */
23 printf(‘‘n The modulus is = %d’’,mod);/*display the output */
24 getch();
25 }
3.1.2 Floating point arithmetic
When an arithmetic operation is preformed on two real numbers or fraction num-
bers such an operation is called floating point arithmetic. The floating point results
can be truncated according to the properties requirement. The remainder oper-
ator (modulo) is not applicable for floating point arithmetic operands. Example,
Let x = 14.0 and y = 4.0 then:
• x + y = 18.0
• x − y = 10.0
• x ∗ y = 56.0
• x/y = 3.50
3.1.3 Mixed mode arithmetic
When one of the operand is real and other is an integer and if the arithmetic
operation is carried out on these 2 operands then it is called as mixed mode
arithmetic. If any one operand is of real type then the result will always be real
thus 15/10.0 = 1.5.
3.2 Relational and Logical Operators
3.2.1 Relational Operators
A simple relational expression contains only one relational operator and takes the
following form:
expr_1 RelationalOperator expr_2
3-3

32. 3 Operators and Expressions
Table 3.2: Relational Operators
Operator Meaning Example Result/ Re-
(x = 1, y = 2) mark
< is less than 1 < 2 TRUE
<= is less than or equal to 1 <= 2 TRUE
> is greater than 1 > 2 FALSE
>= is greater than or 1 >= 2 FALSE
equal to
== is equal to 1 == 2 FALSE
!= is not equal to 1 != 2 TRUE
Relational expressions are used in decision making statements of C language
such as if, while and for statements to decide the course of action of a run-
ning process. Table 3.2 shows the relational operators defined in C with the cor-
responding meaning along with the relational examples.
C has no logical data type with values of TRUE or FALSE. Instead, the value of
zero (0) is used to represent the logical value FALSE, and one (1) is for TRUE. The
expression such as 1 < 2 has a value of 1.
3.2.2 Logical Operators
C has three logical operators for comparing or evaluating the logical and rela-
tional expressions. The common way to show the logical relationships in in a truth
table as shown in Table 3.3.
Examples of the logical operators in the C expressions are given in table 3.4. The
program example for the use of the relational operators is shown in the following
source code.
1 #include<stdio.h>
2 #include<conio.h>
3 /* tell the compiler the start of the program */
4 int main(){
5 //declaration of variables
6 int x,y,z;
7 x = 2; y = 20;
3-4

33. 3.2 Relational and Logical Operators
Table 3.3: Logical Operators Truth Table
Operator x y x AND y Operator x y x OR y
false false false false false false
false true false false true true
AND OR
true false false true false true
true true true true true true
Operator x NOT x
false true
NOT
true false
Table 3.4: Examples of Logical Operators in C
a b Expr1 x y Expr2 Expr1 Operator Expr2 Value
1 2 a < b 10 20 x == y a < b && x == y
1 0 1 && 0 0
1 0 a < b || x == y
1 || 0 1
8
9 clrscr();/* make screen clear */
10 z = x + y; /*arithmetic addition */
11 printf(¸n %d + %d = %dˇ, x,y,z); /*display x+y=z */
S T
12
13 /* relational operator */
14 z = (x < y);
15
16 printf(¸n %d < %d = %dˇ, x,y,z); /* display x<y = z */
S T
17
18 z = x == y;
19
3-5

34. 3 Operators and Expressions
20 printf(¸n %d < %d == %dˇ, x,y,z); /*display x == y = z*/
S T
21 getch();/* hold on screen before enter */
22 return 0;
23 } /* end of program */
The output of the program example is:
2 + 20 = 22
2 < 20 = 1
2 == 20 = 0
3.3 Assignment Operators
Assignment expression evaluates the operand on the right hand side of the oper-
ator (=) and places its value in the variable on the left. The assignment expression
has a value and a result.
3.3.1 Simple Assignment
This is a assignment form found in algebraic expression. Examples of the assign-
ment statements:
a = b; z = x * y; i = i + 1;
The left-hand side operand in an assignment expression must be a single vari-
able. So, it is not allowed to write x * y = z, why?.
3.3.2 Compound Assignment
Compound assignment is a shorthand notation for a simple assignment. It re-
quires that the left operand be repeated as part of the right expression. There
are five compound assignment operators defined in C.
Table 3.5: Compound Assignments
Compound Assignment Equivalent simple assignment
x *= y x = x * y
x /= y x = x / y
x += y x = x + y
x -= y x = x - y
x %= y x = x % y
3-6

35. 3.4 Increment and Decrement Operators
Table 3.6: Increment and Decrement Operators
Postfix Form Meaning Prefix Form Meaning
a++ Use a first before in- ++a Increment a first, be-
crement by 1 fore use.
a-- Use a first before --a Decrement a first, be-
decrement by 1 fore use.
If a compound assignment is used with a binary expression, the binary expres-
sion is evaluated first. Example:
x *= y - 2
is evaluated as:
x *= x * (y - 2)
3.4 Increment and Decrement Operators
An increment or decrement expression is an unary expression. It has one oper-
ator and one operand. The increment operator (++) adds 1 to its operand. The
decrement operator (--) subtracts 1 from its operand. The operand must be a
scalar value and it is illegal to increment or decrement a constant, structure, or
union.
The postfix increment and decrement operators fetch the current value of the
variable and store a copy of it in a temporary location. The compiler then incre-
ments or decrements the variable. The temporary copy, which has the variable’s
value before it was modified, is used in the expression. In many cases, you are
interested only in the side effect, not in the result of the expression. In these in-
stances, it doesn’t matter whether you use postfix or prefix.
You need to be careful, however, when you use the increment and decrement
operators within an expression.
3.4.1 Side Effects of the Increment and Decrement Operators
The increment and decrement operators and the assignment operators cause
side effects. That is, they not only result in a value, but they change the value of
a variable as well. A problem with side effect operators is that it is not always pos-
sible to predict the order in which the side effects occur. Consider the following
statement:
3-7

36. 3 Operators and Expressions
x *= j * j++;
If j equals 3, what will be the value of x?. It is advisable not to use such an
expression. Examples:
i = k--; /* Stores the value of k in i then decrements k. */
j = l++; /* Stores the value of l in j then increments l. */
i = --k; /* Decrements k then stores the new value of k in i. */
j = ++l; /* Increments l then stores the new value of l in j. */
The following program demonstrates the uses both prefix and postfix increment
and decrement operators:
1 #include <stdio.h>
2 int main(){
3 int j = 5, k = 5, l = 5, m = 5;
4 printf("j: %dt k: %dn", j++, k--);
5 printf("j: %dt k: %dn", j, k);
6 printf("l: %dt m: %dn", ++l, --m);
7 printf("l: %dt m: %dn", l, m);
8 return 0;
9 }
The output of the program is as follows:
j: 5 k: 5
j: 6 k: 4
l: 6 m: 4
l: 6 m: 4
The output shows that the initial values of j and k are used in the first printf().
They also show that l and m are incremented and decremented, respectively,
before the third printf() call.
3.5 Bit Operators
The bit operators access specific bits in an object. ANSI C supports the usual six
bit operators, which can be grouped into shift operators and logical operators.
3.5.1 Bit-Shift Operators
The << and >> operators shift an integer left or right respectively. The operands
must have integer type, and all automatic promotions are performed for each
operand. For example, the program fragment:
short int to_the_left = 53, to_the_right = 53;
3-8

37. 3.5 Bit Operators
Table 3.7: Truth Table for Bitwise Logical AND Operator
Bit of Operand1 Bit of Operand2 AND Relation Result
0 0 0 AND 0 0
0 1 0 AND 1 0
1 0 1 AND 0 0
1 1 1 AND 1 1
short int left_shifted_result, right_shifted_result;
left_shifted_result = to_the_left << 2;
right_shifted_result = to_the_right >> 2;
sets left_shifted_result to 212 and right_shifted_result to 13. The
results are clearer in binary:
0000000000110101 53
0000000011010100 212 /* 53 shifted left 2 bits */
0000000000001101 13 /* 53 shifted right 2 bits */
Shifting to the left is equivalent to multiplying by powers of two:
x << y is equivalent to x ∗ 2y .
Shifting non-negative integers to the right is equivalent to dividing by powers of
2:
x
x >> y is equivalent to y .
2
Make sure that the right operand is not larger than the size of the object being
shifted.
3.5.2 Bit Logical Operators
The logical bitwise operators are similar to the Boolean operators, except that
they operate on every bit in the operand(s). For instance, the bitwise AND op-
erator (&) compares each bit of the left operand to the corresponding bit in the
righthand operand. If both bits are 1, a 1 is placed at that bit position in the result.
Otherwise, a 0 is placed at that bit position.
• Bitwise AND Operator (&)
The bitwise AND operator performs logical operations on a bit-by-bit level
using the following truth table: The following example shows the use of the
bitwise logical AND operator.
3-9

38. 3 Operators and Expressions
Operand Bit Representation
53 00 11 01 01
50 00 11 00 10
53 & 50 00 11 00 00
• Bitwise Inclusive (|) OR
The bitwise inclusive OR operator (|) places a 1 in the resulting value’s bit
position if either operand has a bit set at the position. Example:
Operand Bit Representation
53 00 11 01 01
50 00 11 00 10
53 | 50 00 11 01 11
• Bitwise exclusive OR (^)
The bitwise exclusive OR (XOR) operator (^) sets a bit in the resulting value’s
bit position if either operand (but not both) has a bit set at the position.
Example:
Operand Bit Representation
53 00 11 01 01
50 00 11 00 10
53 ^ 50 00 00 01 11
• Bitwise Complement (~)
The bitwise complement operator (~) reverses each bit in the operand. An
example:
Operand Bit Representation
53 00 11 01 01
~53 11 00 10 10
3.6 Cast Operator
To cast a value means to explicitly convert it to another data type. The syntax of
a cast operator has the form:
3-10

39. 3.7 Operator Precedence
( Data Type ) expression
For example, given the two definitions:
int y = 5;
float x;
The following cast operation casts the value of y to float:
x = (float) y; /* x now equals 5.0 */
3.6.1 Casting Floating-Point Values to Integers
Casting a floating-value to an integer is made by by truncating the fractional
part of the number. For example, the floating-point value 3.712 is converted to
the integer 3, and the floating-point value -504.2 is converted to -504. Another
examples:
float f = 3.700, f2 = -502.2, f3 = 7.35e9;
(int)f => 3
(unsigned int)f => 3
(char)f => 3
(int)f2 => -502 in decimal fffffe0a in hex
(unsigned int)f2 => 4294966794 in decimal
(char)f2 => 10 in decimal 0a in hex
(int)f3 => run-time error
(unsigned int)f3 => run-time error
(char)f3 => run-time error
Converting a large float to a char produces unpredictable results if the rounded
value cannot fit in one byte. If the value cannot fit in four bytes, the run-time sys-
tem issues an overflow error.
3.7 Operator Precedence
Precedence is the order in which the compiler groups operands with operators.
The C compiler evaluates certain operators and their operands before others. If
operands are not grouped using parentheses, the compiler groups them accord-
ing to its own rules. The table 3.8 lists the common used C operator precedence
in highest to lowest precedence:
3-11

40. 3 Operators and Expressions
Table 3.8: Operator Precedence with a highest to lowest order
Class of Operator Operators Grouping
primary () [] -> L to R
(type casting)
sizeof
& (address of)
unary * (dereference) R to L
- (reverse sign)
~ !
++ --
multiplicative L to R
* / %
additive + - L to R
shift << >> L to R
relational < <= > >= left to right
equality == =! L to R
bitwise AND & L to R
logical AND && L to R
logical OR || L to R
conditional ?: R to L
= += -= *=
assignment /= %= >>= R to L
<<= &= ^= |=
comma , R to L
3-12

41. 3.8 Exercises
3.8 Exercises
1 Relational operators
Given the following declaration:
int j = 0, m = 1, n = −1;
float x = 2.5, y = 0.0;
Expression Equivalent Expressions Result
j > m j > m 0
m / n < x (m / n) < x 1
j <= m >= n ?
j <= x == m ?
-x + j == y > n > m ?
x += (y >= n) ?
++j == m != y * 2 ?
Replace the ? sign in each row with the equivalent expression and evaluate
it to to get the right result.
2 Write a program that coverts and prints a user-supplied measurement in
inches into:
(a) foot (12 inches)
(b) yard (36 inches)
(c) centimeter (25.4/inch)
(d) meter (39.37 inches)
3 Given the pseudocode below, write a C program that executes it. Use
floating-point data types for all values.
1 read x
2 read y
3 compute p = x * y
4 compute s = x + y
5 compute total = s^2 + p * (s - x) * (p + y)
6 display x and y
7 display total
3-13

42. 3 Operators and Expressions
4 Write a C program code for the question 1 to verify your answer.
5 Logical operators
Given the following declaration:
int j = 0, m = 1, n = −1;
float x = 2.5, y = 0.0;
Expression Equivalent Expressions Result
j && m (j) && (m) 0
j < m && n < m (j < m) && (n < m) 1
m + n || !j (m + n) || (!j) 1
x * 5 && 5 || m / n ?
j <= 10 && x >= 1 && m ?
!x || !n || m+n ?
x * y < j + m || n ?
(x > y) + !j || n++ ?
(j || m) + (x || ++n) ?
Replace the ? sign in each row with the equivalent expression and evaluate
it to to get the right result.
6 Write a C program code for the question 5 to verify your answer.
3-14

43. CHAPTER 4
Selections
A selection statement alters a program’s execution flow by selecting one path
from a collection based on a specified controlling condition or expression. Using
a selection statement, the order of the computation flow is specified.
4.1 Statements and Block
An expression such as i = 0; or a += i becomes a statement if it is followed
by a semicolon. A compound statement or a block consists of a group of state-
ments that starts and ends with an curly bracket. Syntatically a block is equivalent
to a single statement. Example of a block:
{
i = 0;
a += i;
printf(‘‘%2d : %3d’’,i, a);
}
There is no semicolon after the right curly bracket that indicates the block end.
4.2 if statement
if statement is used for a single selection with the syntax and the corresponding
construct is as follows:
if ( condition )
statement;
nextStatement;
if statement evaluates the value of condition to select either the statement
is executed or not. C executes statement only if condition is true, if false, C falls
through to nextStatement without executing the statement. In C, a nonzero value
4-1

44. 4 Selections
represents true, and a zero value is used to represent a false condition. So, con-
dition tests a numeric value, either 0 or nonzero. The following program fragment
can be used to obtain an absolute value of an integer number by evaluating a
value of x.
x = -2;
if (x < 0) /* (-2 < 0) = (TRUE) = 1 */
x = -x; /* x = -(-2) = 2 */
printf(‘‘x = %3d’’,x); /* display x = 2 */
To remember that the condition must be enclosed in parentheses (). If there are
more than one actions to be performed, they must be grouped into a compound
statement, that is a pair of curly brackets ({}). Example:
x = -2;
if (x < 0){ /* Compound statement */
x = -x;
printf(‘‘nx is initially a negative number: %3d’’,x);
}
printf(‘‘nabsolute value of x = %3d’’,x);
4.3 if - else statement
C implements the double selection with the if - else statement and is consi-
dered as the basic decision statement in the computer programming language.
The if statement is the simplified form of this statement. The syntax and the logic
flow is shown in the figure below:
if ( condition )
statement1;
else
statement2;
nextStatement;
if - else statement makes a decision between two alternatives. The com-
puter selects which statement being executed depends on the value of the
4-2

45. 4.3 if - else statement
condition. If the condition is true (a nonzero value), statement1 is executed,
otherwise statement2 is executed. It is impossible to execute both statements in
the same evaluation. Regardless which statement has been executed, the flow
will continue to the nextStatement. Which statement will be executed by the
following program fragment?:
char gender;
/* set first gender as a girl */
gender = ’w’
if ( gender == ’m’)
printf(‘‘n You are a boy.’’);
else
printf(‘‘n You are a girl.’’);
printf(‘‘n Thank You.’’);
The use of a compound statement is demonstrated by the following program
example. The program arrangements two different integers always in an ascend-
ing order.
1 #include<stdio.h>
Input example:
2 #include<conio.h>
a = 20, b = 5
3 int main(){
min = 20
4 int a, b, min;
if (5 < 20) → true.
5 clrscr();
The input values must
6 printf(‘‘nGive two different numbers:’’);
be swapped.
7 scanf(‘‘%d, %d’’,&a, &b);
8 printf(‘‘%dt%d’’, a, b); min = 5
9 min = a; /* set a minimum */
b = 20
10 if (b < min){
11 min = b; /* swap the values */ a = 5
12 b = a;
Display on the
13 a = min;
screen:
14 printf(‘‘nb is greater than a.’’);
b is greater than
15 printf(‘‘ Change the order.’’);
a. Change the or-
16 }
der.
17 else
The ascending or-
18 printf(‘‘nThe order remain unchanged.’’);
der: 5 20.
19 printf(‘‘nThe ascending order: ’’);
20 printf(‘‘%dt%d’’, a, b); The statement of
21 getch(); the else part is not
22 return 0; executed.
23 }
4-3

46. 4 Selections
4.4 switch statement
The switch statement is a conditional branching statement that selects among
several statements or multiple statements based on constant values. The syntax
and the logic flow of the switch statement is shown as follows:
switch ( expression ){
case constant1:
statement 1; break;
case constant2:
statement 2; break;
default:
statement n;
}
nextStatement;
The expression immediately after the switch keyword must be enclosed in paren-
theses and must be an integral expression. The constant following the case key-
words must be integral constant expressions; that is, they may not contain vari-
ables.
An important feature of the switch statement is that the compiler executes
any statements following the selected case label until a break, goto, or return
statement appears. The break statement explicitly exits the switch construct,
passing control to the statement following the switch statement. With a break
statement the program jump out of the switch statement and continues to the
nextStatement. Since this is usually what you want, you should almost always
include a break statement at the end of the statement list following each case
label.
4.4.1 Evaluation of switch statement
The switch expression is evaluated; if it matches one of the case labels, program
flow continues with the statement that follows the matching case label. If none
of the case labels match the switch condition, program flow continues at the
default label, if it exists. No two case labels may have the same value.
default in the switch statement is not required an it is an optional label. If
the value of the condition expression does not match with any label, the control
transfers outside of the switch statement.
The following example will display the annual weather depending on the con-
dition.
4-4

47. 4.4 switch statement
char weather;
printf(‘‘n Enter s,w,a,p for summer, winter,
autumn, or spring:’’);
scanf(‘‘%c’’, &weather);
switch(weather){
case ’s’: printf(‘‘nIt is summer time’’); break;
case ’w’: printf(‘‘nIt is winter time’’); break;
case ’a’: printf(‘‘nIt is autumn time’’); break;
case ’p’: printf(‘‘nIt is spring time’’); break;
default : printf(‘‘nYou entered a wrong character!’’);
}
printf(‘‘nThank you’’);
The following program part demonstrate how to calculate the parking charge
based on the type of vehicle (’c’ for car, ’b’ for bus, and ’t’ for truck) and the
hours a vehicle spent in the parking lot. The parking rates are below:
Type of vehicle Rate per hour
car RM 2.00
bus RM 3.00
truck RM 4.00
1 char vehicle;
2 short int hours;
3 float charge;
4 const float CAR_RATE = 2.00;
5 const float BUS_RATE = 3.00;
6 const float TRUCK_RATE = 4.00;
7 printf(‘‘nEnter c,b,or t for car, bus, and truck,respectively:’’);
8 scanf(‘‘%c’’, &vehicle);
9 printf(‘‘Hours spent: ’’); scanf(‘‘%hd’’, &hours);
10 switch( vehicle ){
11 case ’c’:
12 charge = hours * CAR_RATE; break;
13 case ’b’:
14 charge = hours * BUS_RATE; break;
15 case ’t’:
16 charge = hours * TRUCK_RATE;
17 }
4-5

48. 4 Selections
18 printf(‘‘nParking charges: RM %5.2f’’, charge);
4.5 else - if statement
The switch statement works only when the values of the case labels are integer.
To handle a multiple selection with a decision on the basis of a value that is not
integral, else - if constructs may be utilized as shown in the figure below:
if (expression 1)
statement 1;
else if (expression 2)
statement 2;
else if (expression 3)
statement 3;
else if (expression n-1)
statement n-1;
else
statement n;
nextStatement;
The sequence of if statements is the most general way of writing a multiple
decision. The expressions are evaluated in order. If an expression is true, the
statement associated with it is executed, and this terminates the whole chain.
The flow continues then to the nextStatement. As always, the code for each
statement is either a single statement, or a group of them in braces. The last
else part handles the “none of the above” or default case where none of the
other conditions is satisfied.
Sometimes the trailing else statement n may be used for error checking to
catch an “impossible” condition. To remember that an else is always associated
with the nearest previous if. The else - if construct is used only when:
• The selection variable is not an integral. The expression has also a boolean
value, true or false.
• The same variable is being tested in the expression.
The following program fragment demonstrates the use of else - if statement
to solve a score – grade relationship problem. You are advised to refer to the
associated flow chart to trace the steps in the source code.
4-6

49. 4.6 Conditional Expressions
1 /* Score -- Grade Relationship */
2 char grade;
3 short score;
4 scanf(‘‘%hd’’,&score);
5 if (score >= 90)
6 grade = ’A’;
7 else if (score >= 80)
8 grade = ’B’;
9 else if (score >= 70)
10 grade= ’C’;
11 else if (score >= 60)
12 grade = ’D’;
13 else
14 grade = ’F’;
15 printf(’’Grade: %c’’, grade);
16 /* Add the missing parts*/
4.6 Conditional Expressions
C provides an alternative to traditional if else for two way selection using an
conditional expression. It has three operands and two operators. Each operand
is an expression. The syntax is as follows:
expression ? expr1 : expr2;
The above statement is equivalent to the construct:
if (expression)
expr1;
else
expr2;
Example:
a = 5, b = 10;
result = a < b : a + b; a -b;
What is the value of result?
4-7

50. 4 Selections
4.7 Exercises
1. If originally x = 0, y = 0 and z = 1, what is the value of x, y and z after
executing the following code?
if (z = x < y){
x += 3;
y -= 1;
}
else
x = y++;
2. If originally x = 0, y = 0 and z = 1, what is the value of x, y and z after
executing the following code?
switch (x) {
case 0: x = 2;
y = 3;
case 1: x = 4;
default: y = 3;
x = 1;
}
3. Construct a flowchart to find out the minimum and maximum value of three
integer numbers. Verify your answer by writing the corresponding program
source code and test it.
4. If originally x = 1, y = 3 and z = 0, what is the value of x, y and z after
executing the following code?
switch (x) {
case 0: x = 2;
y = 3;
break;
case 1: x = 4; break;
default: y = 3;
x = 1;
}
5. Write a program that sorts three integer numbers in an ascending order.
6. Write a program that, given the type of vehicle (’c’ for car, ’b’ for bus, ’t’ for
truck, and ’m’ for motor cycle) and hours a vehicle spent in the parking lot,
displays the parking charge based on the rates shown below:
4-8

51. 4.7 Exercises
Vehicle Charge rate/hr.
motor cycle RM 1.00
car RM 2.50
bus RM 3.50
truck RM 4.50
Use the preprocesssor command define for the charge rates instead of the
memory constant, const. What is the difference between them? If none
of the type of vehicle entered matches with any case label, displays wrong
input.
4-9

53. CHAPTER 5
Repetition
Repetition or looping is one of the basic structured programming concepts. Rep-
etition shows the power of computers in ability to repeat an operation or a series
of operations.
5.1 Concept of a loop
The concept of a loop is shown in Figure 5.1.
Figure 5.1: Loop concept
The loop illustrates the statement is always repeated. It never stops. To ensure
that the action ends after the job is done, we must set a certain condition to
control the loop. This condition checks after each iteration to see either the job
is done or not. If not, it repeats one more time, and if it is done, it exists the loop.
5.2 Pretest and Post–Test Loop
In pretest loop, the condition is checked before the loop starts and at the be-
ginning of each iteration after the first. If the condition is true, the statement is
executed, and if the test condition is false, the loop is terminated and the control
goes directly to the nextStatement.
In the post–test loop, the statement is always executed at least once. At the
end of every iteration, the condition is tested. If the condition is true, the loop
repeats, but if the condition is false, the loop ends, and the control goes to the
nextStatement.
Two steps are required in working with a loop.
1. initialization
The purpose of an initialization is to start the loop. In the pretest loop, the
initial value of the test condition must be true. It is done before the first
execution of the statement.
5-1

54. 5 Repetition
Figure 5.2: Pretest (left) and Post-Test (right) Loop
2. Updating
The purpose of an updating is to repeat the execution of the statement and
to change the condition from true to false. If the condition is always true,
the loop will be infinite, in other word, the program execution does never
stop.
Figure 5.3: Initialization and Updating for Pretest (left) and Post-Test (right) Loop
Updating is done in each iteration, usually as the last action after the statement
execution. If the the statement in the loop is repeated x times, the updating is
also done x times.
The limit test for a loop can be expressed into two categories:
5-2

55. 5.3 Loops in C
1. Event-controlled loop
In this loop, the event changes the control condition or expression of the
loop from true to false. For example, when reading data, reaching the end
of data will change the loop control condition from true to false.
2. Counter-controlled loop
When we know the number of times an action or an operation is to be
executed, we use a counter-controlled loop. We must initialize, update,
and test the counter. The update can be an increment or decrement.
Figure 5.4: Event- and Counter- controlled Loop
5.3 Loops in C
C language has three loop statements: for, while, and do..while. The first two
are pretest loop, and the later is a post-test loop. All of them can be used for
event-controlled loop and counter-controlled loop. The while and do..while
are the most commonly used for event-controlled loop, and for loop is usually
used for counter-controlled loop.
5.4 while Loop
The while statement is a pretest loop. The syntax of the while with its corre-
sponding flow chart are shown in Figure 5.5.
• expression: Any expression.
• statement: This statement is executed when the expression is true. State-
ment can be a single statement or a series of statements that encloses in a
parenthesis {}.
5-3

56. 5 Repetition
while (expression)
statement
nextStatement
Figure 5.5: while Loop and the flow chart
The while statement executes the statements within a loop as long as the
specified condition, expression, is true. The while statement tests expression and
if it is true (nonzero), statement is executed. Once expression becomes false (0),
execution of the loop stops and the program control goes to the nextStatement.
Since expression could be false the first time it is tested, statement may not be
performed even once.
A program Example for while loop:
1 #include <stdio.h>
2 int main(void) {
3 char answer, grade;
4 answer = ’y’;
5 printf(’nn’’’);
6 while (answer == ’y’ || answer == ’Y’) {
7 printf("Enter student’s grade: ");
8 scanf("%c", &grade);
9 printf("nComments: ");
10 switch (grade) {
11 case ’A’:
12 case ’a’: printf("Excellentn"); break;
13 case ’B’:
14 case ’b’: printf("Goodn"); break;
15 default : printf("Invalid graden"); break;
16 } /* end switch */
17 printf("nAgain? ");
18 scanf("%s", &answer);
19 } /* end while loop */
20 }
5-4

57. 5.5 do..while Loop
If the program is executed, the output will be as follows:
Enter student’s grade: B
Comments: Good
Again? y
Enter student’s grade: A
Comments: Excellent
Again? n
5.5 do..while Loop
The syntax of the do..while with its corresponding flow chart are shown in Figure
5.6.
do
statement;
while (expression);
nextStatement
Figure 5.6: do..while Loop and the flow chart
The do statement executes statement within a loop until a specified condition
is satisfied. Unlike the for and while loops, do ˇ while performs statement first
E
and then tests expression. If expression evaluates to nonzero (true), statement
executes again, but when expression evaluates to zero (false), execution of the
loop stops and the program control goes to the nextStatement. This type of
loop is always executed at least once.
Program Example for do..while Loop
The program example calculates the summation of an integer that a user supplies
and the summation of the squares of that integer. Mathematically, the summa-
tion can be expressed as follows:
n
sum = i = 1 + 2 + 3 + ... + n
i=1
n ∗ (n + 1)
=
2
5-5

58. 5 Repetition
1 #include <stdio.h>
2 int main(void){
3 int num, sum;
4 char answer;
5 printf("n ");
6 do {
7 printf("Enter an integer: ");
8 scanf("%d", &num);
9 sum = (num*(num+1))/2;
10 printf("The summation of %d is: %dn ", num, sum);
11 printf("nAgain? ");
12 scanf("%c", &answer);
13 }while ((answer != ’n’) && (answer != ’N’));
14 }
If you execute this program, you get the following output:
Enter an integer: 10
The summation of 10 is: 55
Again? y
Enter an integer: 25
The summation of 25 is: 325
Again? n
5.6 for Loop
The for statement is a pretest loop that uses three expressions:
• Initialization
The initialization expression that typically specifies the initial values of vari-
ables. It is evaluated only once before the first iteration of the loop.
• Condition control
The controlling expression determines whether or not to terminate the loop.
It is evaluated before each iteration of the loop. If the condition value is a
nonzero, the statement is executed. If it evaluates to 0, execution of the
statement is terminated and control passes to the nextStatement. This
means that if the initial value of condition becomes zero, the statementis
never executed.
• Update expression
This expression is the increment or decrement expression that typically incre-
ments or decrement the variables initialized in initialization part. It is evalu-
5-6

59. 5.6 for Loop
ated after each iteration of the statement and before the next evaluation
of the condition control expression.
Semicolons separate the expressions in the for loop. Each expression is optional,
but the semicolons must be included. The syntax of the for with its corresponding
flow chart are shown in Figure 5.7.
for (Initial; Condition; Update)
statement;
nextStatement;
Figure 5.7: do..for loop and the flow chart
The for statement can be formulated in while loop and vice versa. The equiv-
alent construct in the while loop is given as follows:
Initial;
while (Condition) {
statement;
Update;
}
nextStatement;
Example how to express the for loop with a while is shown in the following
program fragment:
for (j = 0; j < 10; j++){
printf(‘‘j = %dt’’, j);
if (j % 4 == 0) /* new line */
printf(‘‘n’’);
}
getch();
5-7

60. 5 Repetition
is the same as the following while loop:
j = 0;
while (j<10){
printf(‘‘j = %dt’’, j);
if (j % 4 == 0) /* new line */
printf(‘‘n’’);
j++;
}
getch();
Program Example using for Loop
The following program calculates the permutation of two integer numbers with
the formula:
 
 n  n!
P (n, m) =   =
(n − m)!
m
1 ∗ 2 ∗ ... ∗ n
=
1 ∗ 2 ∗ . . . ∗ (n − m)
1 #include <stdio.h>
2 #define SIZE 10
3 int main(void){
4 int n, m, n_total, m_total, perm, i, j;
5 printf("Enter the numbers for the permutation (n things ");
6 printf("taken m at a time)nseparated by a space: ");
7 scanf("%d %d", &n, &m);
8 n_total = m_total = 1;
9 for (i = n; i > 0; i--) /* compute n! */
10 n_total *= i;
11 for (i = n - m; i > 0; i--) /* compute (n-m)! */
12 m_total *= i;
13 perm = n_total/m_total;
14 printf("P(%d,%d) = %dnn", n, m, perm);
15 }
If you execute this program, you get the following output:
Enter the numbers for the permutation (n things taken m at a
time) separated by a space: 4 3
P(4,3) = 24
5-8

61. 5.7 continue Statement
5.7 continue Statement
continue belongs to the jump statements. The continue statement halts execu-
tion of its enclosing for, while, or do/while loop and skips to the next iteration
of the loop. In the while and do/while, this means the condition expression
is tested immediately, and in the forloop, the update expression (if present) is
evaluated. The effect of the continue statement is illustrated in the Figure 5.8.
Figure 5.8: The continue statement in the loop
The following program fragment calculates the sum of only odd numbers:
const int MAX = 10;
int i, sum = 0;
for (i = 0; i < MAX; i++){
if (i % 2) /* even number? yes, then */
continue; /* jump to i++ */
sum += i;
}
printf(‘‘sum = %3d’’,sum);
5-9

62. 5 Repetition
5.8 Exercises
1. What would be printed from each of the following program segment?
a) while loop:
x = 12;
while(x > 7){
printf(‘‘%dn’’, x);
x--;
}
b) for loop:
for (x = 12; x > 7; x--){
printf(‘‘%dn’’, x);
}
c) do..while loop:
x = 12;
do{
printf(‘‘%dn’’, x);
x--;
}while(x > 7)
2. What will be printed from the following program segment?
for (x = 10; x >= 1; x--){
for (y = x; y >= 2; y--){
printf(‘‘%3d ’’, x);
printf(’’n’’);
}
3. Write a program that creates the following pattern:
1 2 3 4 5 6 7 8 9
1 2 3 4 5 6 7 8
1 2 3 4 5 6 7
1 2 3 4 5 6
1 2 3 4 5
1 2 3 4
1 2 3
1 2
1
5-10

63. 5.8 Exercises
4. Write a for loop that will produce each of the following sequences:
a) 6, 8, 10, 12,..., 66
b) 7, 9, 11, 13,..., 67
c) The sum of the numbers between 1 and 15 inclusive
d) The sum of even numbers between 10 and 40 inclusive.
5. Write a program that prompts the user to enter an integer, n, and then n
real numbers. As the numbers are read, the program will calculate the sum
and the average of the positive numbers.
The program repeats again from the beginning. The program terminates
only if the user enter an ’n’ or ’N’ as the answer.
6. Euler’s number, e, is used as the base of natural logarithms. It can be ap-
proximated using the following formula:
1 1 1 1 1 1
e=1+ + + + + ... + + +
1! 2! 3! 4! (n − 1)! n!
5-11

65. CHAPTER 6
Functions
6.1 Top-Down Design
A program is divided into a main module and its related modules. The division
of modules proceeds until the module consists only of elemantary processes and
cannot be further sibdivided. This process is known as factoring. The top-down
design is illustrated using a structure chart as shown in Figure 6.1.
Terminology:
• Main Module: Calling module. It has submodules, Module 1, 2, and 3.
• Called Module: Module 1, 2, and 3.
Communication between the main module and its submodules is allowed
only through a calling module. If Module 1 needs to send data to Module 2,
the data must be passed through the calling module. No communication
takes place directly between the submodules that do not have a calling–
called relationship.
Figure 6.1: Top-down Design
Two techniques are used for the passing data to a module:
1. Pass By Value
In this technique, a copy of the data is made and the copy is sent to the
called module. The original data in the calling module cannot be changed.
2. Pass By Reference
The calling module sends the address of the data to the called module. In
this case, the called module can change the original data in the calling
module.
6.2 Functions in C
• Top-down design is implemented using functions. A C program consists of
one or more functions. One and only one of the functions must be named
6-1