A computer system is one that is able to take a set of inputs, process them and create a set of outputs. This is done by a combination of hardware and software.
The computer system has one or more inputs to provide data. This data is then processed in some way. The outcome of the processing is sent to an output or it may be stored until some event happens to cause it to be output.
The blue-print of a computer can be shown as :
The Computer System is mainly divided into four parts:
- Input devices.
- CPU (Central Processing Unit).
- Output Devices.
- Storage device.
Precisely, we all know about the input & output devices which are hardware components that we sense them.
While coming to the CPU, this CPU is mainly divided into three categories:
- Memory Unit.
- Control Unit.
- Arithmetic & Logic Unit (ALU).
The Memory Unit is the part of the computer that holds data and instructions for processing.Although it is closely associated with the CPU, in actual fact it is separate from it.Memory associated with the CPU is also called primary storage, primary memory, main storage, internal storage and main memory.When we load software from a floppy disk, hard disk or CD-ROM, it is stored in the Main Memory. There are two types of memory in a computer. They are:
- RAM.
- ROM.
RAM stands for Random Access Memory.This is really the main store and is the place where the programs and software we load gets stored. When the Central Processing Unit runs a program, it fetches the program instructions from the RAM and carries them out.If the Central Processing Unit needs to store the results of calculations it can store them in RAM.Random Access Memory can have instructions READ from it by the CPU and also it can have numbers or other computer data WRITTEN to it by the CPU.The more RAM in your computer, the larger the programs you can run.When we switch a computer off, whatever is stored in the RAM gets erased.The following is a photo of a common RAM chip.
ROM stands for Read Only Memory.The CPU can only fetch or read instructions from Read Only Memory (or ROM). ROM comes with instructions permanently stored inside and these instructions cannot be over-written by the computer's CPU.ROM memory is used for storing special sets of instructions which the computer needs when it starts up.When we switch the computer off, the contents of the ROM does not become erased but remains stored permanently. Therefore it is non-volatile.
The Control unit is a component of a computer's central processing unit (CPU) which directs operation of the processor. It controls communication and co-ordination between input/output devices. It reads and interprets instructions and determines the sequence for processing the data.
It directs the operation of the other units by providing timing and control signals. All computer resources are managed by the CU (Control Unit). It directs the flow of data between the Central Processing Unit (CPU) and the other devices. The control unit was historically defined as one distinct part of the 1946 reference model of Von-Neumann architecture. In modern computer designs, the control unit is typically an internal part of the CPU with its overall role and operation unchanged.
The functions of CU are:
- Controls sequential instruction execution
- Interprets instructions
- Guides data flow through different computer areas
- Regulates and controls processor timing
- Sends and receives control signals from other computer devices
- Handles multiple tasks, such as fetching, decoding, execution handling and storing results
Arithmetic Logic Unit, ALU is one of the many components within a computer processor. The ALU performs mathematical, logical, and decision operations in a computer and is the final processing performed by the processor. After the information has been processed by the ALU, it is sent to the computer memory.In some computer processors, the ALU is divided into two distinct parts, the AU and the LU. The AU performs the arithmetic operations and the LU performs the logical operations.
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