In PC INPUT is usually performed using the keyboard. The process is performed by the computer which in some cases may be in same unit as the keyboard. The output is projected onto a visual display unit or monitor screen.
Any digital Computer system can be thought of has been made of two parts; Hardware and Software. In the following paragraphs we will discuss in some details what constitutes hardware and software. There is also a small but important part called firmware. All these will now be discussed.
HARDWARE COMPONENTS OF A COMPUTER
Computer hardware consists of the various mechanical, electrical, electronic and magnetic parts of a computer. A simplified model of a typical micro computer hardware subsystem is illustrated below:
INPUT UNIT
Input unit consists of devices through which information to be processed is presented to the computer. Such devices transform source data into internal form which are transmitted to the primary memory.
ALU - Arithmetic and Logical Unit
CPU - Central Processing Unit
Examples of input unit includes keyboard on a terminal which might also have visual display unit, floppy disk units, scanners, magnetic tape units, and analog-to-digital converters. Others may include microphones which can convert speech into data which the computer can process, and card readers which read data from coded punch cards.
MEMORY SYSTEM
The memory system of a computer is made up of the primary memory and secondary memory. For a PC, the primary memory is mainly made up of RAM and some ROM.
The primary memory contains the programs and data being processed at any given time. It is smaller in size than the secondary memory. In addition, it is volatile, in that its content is lost when there is a power failure or when the computer is shut down. It is however much faster than the secondary memory.
Secondary or auxiliary memory, or backup memory or storage is a supplement of primary memory. It usually holds programs and data files for both processed and unprocessed information and would have slower but larger capacity storage when compared with primary memory.
The continued need for secondary memory despite the fact that modern computers tends to have large main memory can be explained by two major considerations. In the first place, main memory is still not large enough to deal with the volume of data and large number of different instructions which the information processing needs modern organisation demand. Secondly, in cases of power failure, the contents of the main memory of a computer are erased. All data and instructions currently residing there are therefore lost. A very large capacity secondary storage medium capable of retaining data and instructions in a permanent form is therefore needed.
Whenever necessary appropriate section of the stored items can be copied back into the memory for further or repeat processing. Both data and information can be written, stored, and read as many times as possible.
NOTE: Data and information are stored in memories in Bytes. A Byte is used to store one character. A Byte is made up of 8BITs. A Bit is either a 0 or 1. A memory with a capacity of 100 bytes can store 100 characters. Similarly, a memory with a capacity of 1000 bytes can store approximately 1000 characters. 1 Kb is actually 1024 Bytes. 1 Megabyte is approximately 1 Million bytes.
The following are the most commonly used secondary storage system:
Magnetic Tape Unit
These have very high storage capacity and are very reliable. Retrieval time is however literally slow but still fast enough to be useful for most backup needs. They are expensive and are therefore found mostly with large expensive computer installations.
Exchangeable Disk Units
These have very high capacity, allow very quick retrieval of items, and are very reliable. They are also very expensive and are therefore used with larger computer system.
Diskette Unit
Are very popular with personal computers. They have much smaller capacity and are rather less reliable. Retrieval of items is slow but they are inexpensive.
Note: When discussing peripherals it is important to distinguish between the medium used by the Peripheral device and the device itself. As an example magnetic tape is in medium used by a peripheral device, the tape drive, to store data. Magnetic tape is therefore not a storage device. In order to avoid any confusion we may consider media as a consumable used in conjunction with the device.
Multiplexors are peripheral devices, which collect data and instructions from a number of terminals, concatenate them that is link them together and send to a CPU than a single communication channel. Conversely, data and instructions from the CPU are disseminated to the terminal in the opposite direction.
CPU
The central processing unit is the heart of any digital computer system. It is split into three distinct parts each of which performs a distinct function. The parts includes an arithmetic and logical unit, control unit and Primary or main memory. The ALU is the only place in the computer system where processing is carried out. Although modern computers have very large memory capacity yet it is still not possible to perform one operation or process at one time.
OUTPUT UNIT
Output unit transformed processed information from its internal form into ordinary readable form. Examples of Output unit includes printer, plotters, digital-to-analogue converters, and speaker system.
Note:
• It must be emphasized that printer is not the only output device. Technology has now developed to a stage where voice input and output has become practical. Furthermore, computers can now be used to project three-dimensional images which appears in the form of holograms.
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| A printer, Output device |
• The input unit, Output unit, and the secondary memory are sometimes referred to as peripheral or peripheral devices. This is because they are considered as additional devices which are attached to the CPU.
SOFTWARE COMPONENTS OF A COMPUTER
Computer software is the collective term for all programs which controlled activities of a computer. A program is basically a sequence of instructions that is given to a computer to guide it in processing information.
Two categories of programs can be identified. These are SYSTEMS programs and APPLICATION PROGRAMS.
SYSTEM SOFTWARE
System programs and programs usually but not necessarily furnace to buy computer manufacturer which contributes to the proper control and enhanced performance of the computer system. Examples of system software include Operating Systems (OS), Utilities, Translators, and Editors.
OPERATING SYSTEM
Operating Systems, are formed by a suite of programs which takes control over the operations of the computer to the extent of being able to allow a number of programs to be run on the computer without human intervention. Some of the functions of operating system includes, allowing users to share data amongst themselves, scheduling and loading of programs to provide for continuous processing, control over selection and operation of input and output devices, loading of programs and subway things into primary memory as and when required, allocation of memory is to programs and data files, passing of control from one job to another under a system of priority. Thus, the OS is not only in memory management but also in process Management, and Information Management.
It may be necessary to realise that memory is made up of locations each of which has a unique address. Each location can contain data or programs. It is therefore possible to know the point at which each item in memory starts and ends.
CONCLUSION
From our discussion so far can be deduced that when one buys a computer, the very first program that should be installed on it is the operating system. We have also been able to see all the computer system setup which includes the hardware and software.
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