1. Storage Devices

8. RAM vs ROM Data is safe when PC is switched off Data is lost when PC is switched off Information inside cannot be changed Data can be changed Stores information permanently Stores information temporarily Read Only Memory Random Access Memory ROM RAM

10. Advantages and Disadvantages Fairly fast to access the data Slower to access than the hard disk Most computers can read CDs. Smaller storage capacity than a hard drive or DVD Very cheap to produce Fairly fragile, easy to snap or scratch Small and portable Disadvantages Advantages

12. Advantages and Disadvantages It is fixed inside the computer and cannot easily be transferred to another computer Cheap on a cost per megabyte compared to other storage devices Regular crashes can damage the surface of the disk, leading to loss data in that sector Stored items are not lost when you switch off the computer Can crash which stop the computer from working Stores and retrieves data much faster than a floppy disk Far slower to access data than ROM and RAM chips Large storage capacity Disadvantages Advantages

14. Advantages and Disadvantages Many new computers don’t have floppy disk drives Small Storage capacity Can be used many times Can transport viruses from one machine to another Security tab to stop data from being written over Quite slow to access and retrieve data Useful for transferring small files Data can be erased if the disk comes into contact with a magnetic field Inexpensive Not very strong - easy to damage Portable - small and lightweight Disadvantages Advantages

16. Advantages and Disadvantages Being developed with fashionable looking casing More reliable than floppy disk If handled roughly, it can be damaged Hold more data than floppy disk or even a CD Can be easily be lost More compact, portable and cheap Disadvantages Advantages

17. BINARY CODE

19. Units Used A 1 or 0 (b) 1 bit 1 nybble (?) 4 bits 1 byte (B) 8 bits 1,125,899,906,842,624 bytes 1 petabyte (PB) 1,099,511,627,776 bytes 1 terabyte (TB) 1,073,741,824 bytes 1 gigabyte (GB) 1,048,576 bytes 1 megabyte (MB) 1,024 bytes 1 kilobyte (KB) Equivalent Unit

22. ASCII to binary Spare the jokes, when we enter a word example, “Computer”, it will program as: 0100001101101111011011010111000001110101011101000110010101110010 0111 0010 0101 0010 0110 0001 0100 0001 Binary ‘ r’ ‘ R’ ‘ a’ ‘ A’ ASCII