1. Introduction to Computers and
Programming (CSC103)
Lecture 04

2. 2
void main (void)
{
printf("Testing...n..1n...2n....3n")
}
Compilation Result?
#include <stdio.h>
void main (void)
{
value1 = 50;
value2 = 25;
int value1, value2, sum;
sum = value1 + value2;
printf("The sum of %d and %d is %dn", value1, value2, sum);
}
Compilation Result?
1
2

3. 3
#include <stdio.h>
void main (void)
{
printf ("Testing...n..1n...2n....3n");
}
Output?
#include <stdio.h>
void main (void)
{
int value1, value2, sum;
value1 = 50;
value2 = 25;
sum = value1 + value2;
printf("The sum of %d and %d is %dn", value1, value2, sum);
}
Output?
1
2

4. Arithmetic Instructions in C
4
int ad ;
float kot, deta, alpha, beta, gamma;
ad = 3200 ;
kot = 0.0056 ;
deta = alpha * beta / gamma + 3.2 * 2 / 5 ;
---------------------------------------------------------------------------------
Here,
*, /, -, + are the arithmetic operators.
= is the assignment operator.
2, 5 and 3200 are integer constants.
3.2 and 0.0056 are real constants.
ad is an integer variable.
kot, deta, alpha, beta, gamma are real variables.

5. Variable Declaration and Use
5
Correct Incorrect
float a = 1.5, b = a + 3.1; float b = a + 3.1, a = 1.5;
int a, b, c, d ;
a = b = c = 10 ;
int a = b = c = d = 10;
int x, y, z;
x = y * z;
int x, y, z;
y * z = x;
Cannot Use aVariable before declaring it!

6. Integer and Float Conversion
6
 Implicit and Explicit Conversions
 An arithmetic operation between an integer and integer
always yields an integer result.
 An operation between a real and real always yields a real
result.
 An operation between an integer and real always yields a real
result. In this operation the integer is first promoted to a real
and then the operation is performed. Hence the result is real.

7. 7
int i ;
float b ;
i = 3.5 ;
b = 30 ;
 What would be the value of i and b?
 Think of Integer and Float Conversion

8. 8
 k is an integer variable
 a is a real/float variable

9. Receiving User Input
 To get the input from the user we use a library function called
scanf()
 The format of scanf() is;
scanf(“<format specifier>”, &<variable name>);
 format specifier shows what type of data you want to input or get
from user
 & before the variable name is must
 & is an “Address of Operator”
 It gives the location number used by the variable in memory
 &num tells the scanf() function at which memory location should
it store the value supplied by the user
 a blank, a tab or a new line (pressing enter) must separate the values
supplied to scanf()
Example: scanf(“%d %d %f”, &p,&n,&r);
9

10. Example
#include<stdio.h>
void main()
{
int num;
printf(“Enter an Integer: ”);
scanf(“%d”, &num);
printf(“You entered the number %d”, num);
}
Output?
10

11. Example # 2
11
#include<stdio.h>
void main()
{
int x, y;
scanf("%d%d",&x,&y);
printf(“You have entered x=%d, y=%d",x,y);
}
Output?

12. Evaluate yourself!
12
 Point out the errors, if any, in the following C statements:
(a) int = 314.562 * 150 ;
(b) name = ‘Ajay’ ;
(c) varchar = ‘3’ ;
(d) 3.14 * r * r * h = vol_of_cyl ;
(e) k = ( a * b ) ( c + ( 2.5a + b ) ( d + e ) ;
(f) m_inst = rate of interest * amount in rs ;