The Basic Action of a Computer
The parts of computer can be connected in different ways. In some designs, the processor is central. In others, the memory is central. In many modern designs, all the parts are equally important. A common type of operation is shown in the Fig. 4.
Fig. 4. Operation of computer.
It is shown that the processor is central in this organisation. All movement of data is through the processor.
When the memory is central, moving data from an input device to memory requires two instructions:
1. Move input data to the processor. Inside the processor, the data is held in a place called register.
2. Move data from the register to memory.
Computer memory is used to hold instructions as well as data. Memory is divided into parts called locations. Locations normally hold 8, 16, or 32 bits. All locations in one computer hold the same number of bits. The data or instruction is represented by the pattern of bits. Each location has a number called an address. All instructions involving memory require an address.
Machine language
Large numbers of bits are stored electrically in the processor and memory. Some of the patterns of bits are instruction codes. Other patterns of bits are addresses of input data. These addresses tell the computer where to get its data. Again, other patterns of bits are addresses of output data. The entire set of instruction codes and addresses is known as a machine language program.
Machine language programs appear as complex patterns of bits. These patterns are difficult for programmers to read. Such patterns are also difficult to correct or write by hand. In addition, different types of computers have different machine languages. Each machine language specifies behaviour inside a particular CPU. For this reason, machine language is called
low-level language. To write a program in a machine language, the programmer must understand all the details of the computer's design.
To make the work of a programmer easier, programming languages were invented. Programming languages do not use binary digits. Some programming languages use English words. An example of one programming language is COBOL.
To write a program in COBOL, the programmer does not need to know all the details of the computer's design. A COBOL program written for one type of computer is very similar to a COBOL program written for another type of computer. For this reason, programming languages like COBOL are known as high-level languages.
Computers can only execute machine language programs. They cannot execute the COBOL statements written by the programmer The COBOL program must first be translated into machine Language. This translation is carried out by a special program called a compiler.
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Computer memory is used to hold data and ...
Memory is divided into . ..
Bach Location has ...
All instructions require . ..
The entire set of instruction codes and addresses is known as ...
Computers can only execute ...
A special program called ... carries out a translation.
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