SECTION 1
FUNDAMENTALS OF HARDWARE AND SOFTWARE
A computer is an electronic device, operating under the control of instructions stored in its memory.
 Input – accept data
 Processing – manipulate data
 Output – produce results from the processing
 Storage – store the data and results for future use

HARDWARE
Hardware is the physical parts of the computer. There are five main components:
1. Central Processing Unit
2. Primary Storage devices
3. Secondary Storage devices
4. Input Devices
5. Output Devices
1. The Central Processing Unit (CPU) is also known as the processor. It is the brain of the computer and converts data into information. CPU speed is measured in Hertz.
1 hertz = 1 clock cycle/machine instruction per second
1 Kilohertz (KHz) = 1000 Hz
1 Megahertz (MHz) = 1000 KHz = 1 000 000 Hz (1 million)
1 Gigahertz (GHz) = 1000 MHz = 1 000 000 000 Hz (1 billion)
A CPU with speed of 1 GHz can execute 1 billion machine instructions per second.
There are two main parts of the CPU:
A: Control unit – This controls the sequencing of operations of the CPU by fetching and decoding instructions and coordinating the input and output devices.
B: Arithmetic Logic Unit (ALU) – This manipulates the data. It performs arithmetic operations
(including addition, subtraction, division and multiplication and logical operations (including reasoning and performing the comparisons necessary to make decisions).

2. Main Memory/Immediate Access Storage (IMAS)/Primary Storage – This is storage that is directly available to the CPU. It is located directly on the computer's circuit board so that data can travel quickly to and from the
CPU. Two main types of main memory chips are RAM and ROM.
3. Secondary storage–This is needed for the permanent storage of data so that it can be used later. Secondary storage devices include floppy drives, hard drives, CD/DVD drives and tape drives.
4. Input devices – These are devices that accept data and convert it into a form the computer can understand.
5. Output devices – These are devices that display the resulting information in a form the user can understand. PRIMARY STORAGE
Bistable device – This is a device that is stable in only one of two states. Everything the computer does is as a result of turning on and off different combinations of microelectronic switches called transistors (bistable device). The on and off of the transistors are used to represent 0s and 1s that make up the binary number system. These 0s and 1s are known as bits.

Function

Volatility
Access
Length of storage
Content

Random Access Memory (RAM)
Stores data and instructions that are in current use by the CPU.

Read Only Memory (ROM)
Stores data and instructions that are necessary to boot up or restart the computer. It is volatile.
It is non-volatile.
Allows data to be read from and Only allows data to be read from it. written to it.
It stores data temporarily.
It stores data permanently.
Content is determined by the Content is determined by the programs that are currently being manufacturing process. It also contains used. basic input/output instructions.

Random Access Memory (RAM)
 The size of the RAM varies between 128Mb, 256Mb, 512 Mb, 1,024 Mb (1Gb), 2,048 Mb(2Gb), 3,072
Mb(3Gb) etc.
 RAM can be randomly accessed. This means data from any location in RAM can be accessed as needed.  One advantage of RAM is that CPU can access data held in RAM almost immediately.
Volatile means that the data held is lost when the computer is turned off.

Programmable Read Only Memory (PROM)
 This is a type of chip that is manufactured blank and allows data to be written onto it once.
 After a PROM has been programmed, it is dedicated to that data, and it cannot be reprogrammed.
 Because ROMs are cost-effective only when produced in large volumes, PROMs are used during the prototyping stage of the design. New PROMs can be created and discarded as needed until the design is perfected.
Eraseable Programmable Read Only Memory (EPROM)
 This is a type of chip that allows data to be written to it after it has been manufactured.
 The data can then be erased using ultra-violet light and reprogrammed.
 Although EPROMs are more expensive than PROMs, they can be more cost-effective in the long run if many changes are needed.

Units of Storage


Bit - stands for Binary DigIT. A bit is a bistable device - it can either be a 1 or a 0. It is the smallest unit of storage.



Byte - grouping of 8 bytes. It is used to represent one character (a-z, A-Z, 0-255, typographical symbols).
1 kilobyte (KB)
1 megabyte (MB)
1 gigabyte (GB)
1 terabyte (TB)

= 1024 bytes
= 1024 KB
= 1024 MB
= 1024 GB



Word – the amount of data that can be accessed by the CPU from RAM at one time (one cycle).



Word size - the amount of bits in a word.