Page 19 - DCAP102_DCAP_401_Foundations of Computer Programming

Basic Programming Skills/Foundations of Computer Programming

Notes 100111100011101100110101

101100010101010101110000
000000000000000000000000
This is obviously not a very easy language to learn, partly because it is difficult to read and

understand and partly because it is written in a number system with which we are not familiar.
But it will be surprising to note that some of the fi rst programmers, who worked with the fi rst
few computers, actually wrote their programs in binary form as above.
Since human programmers are more familiar with the decimal number system, most of them
preferred to write the computer instructions in decimal, and leave the input device to convert
these to binary. In fact, without too much effort, a computer can be wired so that instead o fusing
long numbers. With this change, the preceding program appears as follows:
10001471
14002041

30003456
50773456
00000000
The set of instruction codes, whether in binary or decimal, which can be directly understood by
the CPU of a computer without the help of a translating program, is called a machine code or
machine language. Thus, a machine language program need not necessarily be coded as strings
of binary digits (1s and 0s). it can also be written using decimal digits if the circuitry of the
computer being used permits this.

Advantages and Limitations of Machine Language

Programs written in machine language can be executed very fast by the computer. This is mainly
because machine instructions are directly understood by the CPU writing a program in machine
language has several disadvantages which are discussed below.
1. Machine dependent: Because the internal design of every type of commuter is different from
every other type of computer and needs different electrical signals to operate, the machine
language also is different from computer to computer. It is determined by the actual design
or construction of the LU, the control unit, and the size as well as the word length of the
memory unit. Hence, suppose after becoming proficient in the machine code of a particular

computer, a company decides to change to another computer, the programmer may be
required to learn a new machine language and would have to rewrite all the existing
programs.

2. Diff cult to program: Although easily used by the computer, machine language is diffi cult to
program, it is necessary for the programmer either to memorize the dozens of code numbers
for the commands in the machine’s instruction set or to constantly refer to keep track of the
storage location of data and instructions. Moreover, a machine language programmer must
be an expert who knows about the hardware structure of the computer.

3. Error code: For writing programs in machine language, since a programmer has to remember
the opcodes and he must also keep track of the storage location of data and instructions,

it becomes very difficult fro him to concentrate fully on the logic of the problem. This
frequently results in program errors. Hence, it is easy to make errors while using machine
code.

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