# Computer Software and Hardware

#### Chapter 4

5 Steps - 3 Clicks

# Computer Software and Hardware

### Introduction

A computer system consists of two major elements: Computer Software and Hardware. Computer hardware is the collection of all the parts you can physically touch. Computer software, Software is a set of instructions for a computer to perform specific operations.

### Concepts

CPU is the main component of the computer. CPU is divided into three major parts.

Control unit
This unit controls the operations of all parts of a computer. It obtains the instructions from the memory, interprets them, and directs the operation of the computer. CPU communicates with Input/output devices for transfer of data or results from storage and it does not process or store data.

• It controls all units of computer when data is entered by keyboard, it saves the instructions given by user and send to the ALU to further process.

• It converts the user input and coverts them into signals sends ALU.

• It uses clock inputs to maintain the sequence of the data, this speed is the frequency of the data processing and it is measured in Megahertz.

Arithmetic Logic Unit
An arithmetic-logic unit (ALU) is the part of a computer processor (CPU) that carries out arithmetic and logic operations. Modern CPUs contain very powerful and complex ALUs. In addition to ALUs, modern CPUs contain a control unit (CU).

• An ALU performs basic arithmetic, examples of arithmetic operations are addition, subtraction, multiplication, and division.

• It also performs logical operations like comparisons of values such as NOT, AND, and OR.

• All information in a computer is stored in the form of binary numbers, i.e. 0 and 1.

• All arithmetic operations are carried out by using the gates. There are many types of gates are there NOR, AND, NOT, OR and etc.

• ALU splits complex operations into simple operations to perform the task easily.

Truth table of logical gates

Input Output
A B AND NAND OR NOR EXOR ENOR
0 0 0 1 0 1 0 1
0 1 0 1 1 0 1 0
1 0 0 1 1 0 1 0
1 1 1 0 1 0 0 1

Memory Unit
The memory unit stores the data, instructions and sends the information to all the other units of the computer whenever it needs. It is also known as primary memory or main memory or RAM (Random access memory) or internal storage unit. All input and output are transmitted through main memory.

Primary Memory
It is also called as the main memory of the computer. It stores the instructions, operating system and data which required to run the computer. Examples of primary memory are RAM.

Secondary Memory
Secondary storage, sometimes called auxiliary storage or external storage, is storage. It is not volatile memory and is not directly accessed by the computer. We can store the data in this longer period until we format the data it will be available.

Secondary memory consists of all permanent storage devices like read-only memory (ROM), flash drives, hard disk drives (HDD), magnetic tapes and other types of internal/external storage devices

• Secondary memory is slower than primary memory but can store and retain data whenever user needs.

• User can store huge amount of data ranging from megabytes to several terabytes of storage space within a single memory.

• User can carry these devices in anywhere and can connect to any device.

Hardware peripherals of computer
The peripheral devices connect to the computer to extend the features and to extend the functionality of the devices. Examples are a mouse, keyboard, monitor, printer, and scanner.

Input devices
Input devices are used to give instructions to the computer to perform the operations. Examples of input devices are a mouse and a keyboard.

Output devices
Output devices are used to see the results of the input which is given by the user. Examples of output devices are monitor and a printer

Storage devices
Storage devices are used to store the information and data. Examples of storage devices are the hard drive, pen drives, DVDs, CDs etc.

### Questions

1. Which one of these holds RAM, ROM, and extension cards?

1. Hard disk
2. D-ROM
3. Floppy disk
4. Motherboard

2. What is external memory called?

1. Primary memory
2. Secondary memory
3. Random access

3. Main memory stores_______.

1. Data
2. Program
3. Results
4. All the above

4. A CD-ROM is ______.A)an optical ROM

1. an optical ROM
2. an erasable ROM
3. a magnetic ROM
4. None of the above

5. Diameter of hard disk platter is

1. 4.5″
2. 3”
3. 5”
4. 4.2”

6. How do we measure screen of the monitor?

1. Vertically
2. Horizontally
3. Internally
4. Diagonally

7. Which bus is bidirectional?

1. data bus
2. control bus
4. multiplexed bus

8. Information retrieval is fastest from

1. Hard disk
2. CD-ROM
3. Floppy disk
4. Motherboard

9. Which of these is software?

1. Keyboard
2. Internet Explorer
3. Trackball
4. Scanner

10. Central Processing Unit (CPU) consists of

1. control unit
2. arithmetic and logic unit
3. the main store
4. all of above

11. What is the permanent memory built into your computer called?

1. RAM
2. ROM
3. CPU
4. CD_ROM

12. Which of the following will you require to hear music on your computer?

1. Sound Card
2. Video Card
3. Mouse
4. Joy Stick

13. How many bits are used in the data bus?

1. 7
2. 8
3. 9
4. 2

14. EEPROM can be erased using

1. Electrical charge
2. Magnetic field
3. Ultraviolet rays
4. None of the above

15. Which of these RAMs access data faster?

1. SRAM
2. DRAM
3. DRDRAM
4. RAM

16. Which is memory directly connected to the CPU?

1. Primary memory
2. Secondary memory
3. RAM
4. ROM

17. The various cards in a PC require _______ voltage to function.

1. AC
2. DC
3. Both A and B
4. None of the above

18. Which has more storage capacity?

1. Floppy disk
2. CD
3. DVD
4. Motherboard

19. What type of memory is a PEN driv?

1. FlASH memory
2. Catch memory
3. Both A&B
4. None of the above