THE COMPUTER SYSTEM...

A typical computer system is made up of two basic components. The Hardware and Software.

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The Hardware components are the physical components of the computer which consist of objects that can be touched.
The Software consists of programs and data objects which allow the computer to accomplish a specific task. The software is not physical but their effect can be seen

HARDWARE COMPONENTS
The computer hardware consists of five basic components: Input unit, Output unit, Main memory, Mass memory and Central processing unit (CPU).
Input Unit
This unit converts user's information to the form the Computer can understand and transfers it to the memory. The input device serves as an interface between the user and the Computer. Usually, the input unit converts keyboard strokes and mouse clicks to digital signals (strings of zeroes and ones). E.g of input devices include microphone, mouse, joystick, scanner, keyboard, digital camera etc.
Output Unit
This unit converts computer messages and results of a computer operation into a form that can be understood by the user. They can also be referred to as an interface between the computer and the user. In a digital computer, the output device converts strings to zeroes and ones to a form the user will understand e.g numbers or alphabets. E.g of output devices are loudspeaker, printer, plotter, visual display unit (VDU) etc.
Main Memory (Primary memory)
This is the part of the computer where data and instructions are stored temporarily. Only the most needed data are transferred to the main memory. If the power is off from the computer, the data and the instruction on the main memory will be lost. Any memory device that loses data and instruction stored on it when power is off is called Volatile memory. The main memory is very fast to access, relatively small and not too expensive. Different sections of the main memory can be accessed in a random manner; therefore they are referred to as Random Access Memory (RAM)
Mass Memory
This memory can hold instruction and data for a long period of time. Unlike the main memory which loses instruction and data when power is off, the mass (secondary) memory retains its content when power is off. Any memory device that retains its content when power is off is called a Non-Volatile Memory. They are usually very large and slower. The size of the mass memory ranges from Megabytes to Terabytes. Examples include, hard disk, floppy diskette, magnetic tape, zip drive, paper tape etc.
Central Processing Unit (CPU)
The CPU controls and coordinates all processing operation. It is made up of the following components... Control Unit, Arithmetic and Logic Unit (ALU) and Registers.
i. The Control Unit is the part of the CPU which controls and coordinates the other parts of the system. It determines what is to be done, when and how if would be done. It also determines when instructions are fetched from the memory, when the input device should accept and what should be sent to the output device.
ii. The Arithmetic and Logic Unit is the part of the CPU where basic arithmetic and logical operations are performed. These operations include, addition, subtraction, multiplication, division, exponential and logical operations (AND,OR,NOT).
ii. The Registers are the third component of the CPU, usually a few kilobytes, which facilitate the execution of instructions by acting as temporary areas for instructions and data. Usually, registers can retrieve information, hold it and transfer it very quickly under the control of CPU. Intermediate calculations are known to be performed in registers, and final results transferred back to primary memory.

SOFTWARE COMPONENTS
The collection of programs needed to operate a computer system constitutes the Software component. The hardware components of the computer system cannot work alone. In most cases, the instructions and data with which the hardware will work are processed in specific format and fed into the computer. These data and instructions constitute the software of the computer system. Three broad categories of software are, System Software, Application Software and Translators.
System Software
The basic aim of this category is to eliminate or reduce the problems associated with using and managing the computer resources such as processor, memory and hard disk. System software includes firmware and operating systems. The firmware is software that performs specific tasks in the computer system and embedded in hardware permanently. The Operating system is the software that co-ordinates all application of software on the Computer. Therefore, application programs cannot be used on a Computer until an Operating system is installed. Types of operating system include Single user, Multi user and Network Operating Systems
i. Single User Operating Systems
They are meant for single users at a time and are commonly used on microcomputers. Examples include MSDOS, Window 95/98/2000/XP/7/8, Ubuntu.
ii. Multi User Operating Systems
They are designed to be used by multiple users at a time. Examples include UNIX, LINUX etc.
iii. Network Operating System(NOS)
These are designed mainly to be used in a network environment where independent computer system are linked without necessarily losing their autonomy. NOS are typically Multi user systems. Examples of NOS include Novell Netware, Windows NT, Windows server etc.
iii. Application Software
This is the software written by a user or software vendor to solve specific user problems. Examples are the processors (MS-Word, WordPerfect, OpenOffice etc), Database management software, (DbaseIV, Oracle, MySQL etc), Spreadsheets (Lotus 1-2-3, MS-Excel etc) among others. Utility Programs are a special kind application software used to perform simple but important tasks on the computer such as scanning the hard disk for computer viruses, preventing spyware, formatting disks or checking disks for damages. Most mordern operating systems have some utility programs integrated into it. Examples are Norton antivirus, Windows Defender, McAfee, ScanDisk, PartitionManager etc.
Translators
These are software packages that are used to convert programs written in high level or low level languages into machine codes understandable by the computer. They are software that enable programmers to develop other application software. The basic types of translators are Compilers/Interpreters and Assemblers
i. Compilers
They are used to convert source programs in high level language to machine language or object codes all at once. Interpreters, on the other hand perform the same task but convert the source program on a line by line basis.
ii. Assemblers
They are used to convert source programs in low level language to machine language.