History Of Programming Languages
Just as human beings communicate with each other through the use of languages such as English, Spanish, Hindi, and Chinese, programmers use a variety of special languages called programming lanuages to communicate with the computer . some poputlar programming languages are visual basic, visual C#, c++, VC++, java perl, C, and COBOL( common business oriented language) . In the next sections you follow the progression of programming languages from machine language to assembly languages and then to high level languages.
Machine Languages
Within a computer all data is represented by microscopic electronic switches that can be either off or on . the off switch is designated by a 0, and the on switch I designated by a 1. because computers can understand only these on and off switches the first programmers had to write the program instructions using nothing but combinations of 0s and 1s; for example a program might contain the instruction 00101 10001 10000. Instruction written in 0s and 1s are called machine language or machine code. The machine languages (each type of machine has its own language) represent the only way to communicate directly with the computer. As you can imagine, programming in machine language is very tedious and error prone and requires highly trained programmers.
Assembly Languages
Slightly more advanced programming languages are called assembly languages. The assembly languages simplify the programmer’s job by allowing the programmer to use mnemonics in place of the 0s and 1s in the program. Mnemonics are memory aids – in this case, alphabetic abbreviations for instructions. For example, most assembly languages use the mnemonic ADD to represent an add operations and mnemonic MUL to represent a multiply operation. An example of an instruction written in an assembly language is MUL b1, ax.
Programs written in a n assembly languages require an assembler which also is a program, to convert the assembly instructions into machine code the 0s and 1s the computer can understand. Although it is much easier to write programs in assembly language than in machine language, programming in assembly language is tedious and requires highly trained programmers.
High Level Languages.
High Level languages represent the next major development in programming languages. High-level languages are a vast improvement over machine and assembly languages because they allow the programmer to use instruction that more closely resemble the English language. An example of an instruction written as in a high – level language is grossPay = hours * rate.
Programs written in a high level language require either an interpreter or a compiler to convert the English like instruction into the 0s and 1s the computer can understand. Like assemblers, both interpreter and compilers are separate programs. An interpreter translates the high levels instruction into machine code, line by line as the program is running whereas (in most cases) a compiler translates the entire program into machine code before running the program.
Like their predecessors, the first high-level languages were used o create procedure-oriented programs. When writing a procedure-oriented program, the programmer concentrate on the major tasks that the program needs to perform. A Payroll program, for example, typically performs several major tasks such as inputting the employee data calculating the gross pay, calculating the taxes, calculating the net pay, and outputting a pay check./ the programmer must instruct the computer every step of the way , from the start of the task to its completion. In a procedure – oriented program, the programmer determines and controls the order in which the computer process the instruction s. In other words, the programmer must determine not only the proper instruction to give the computer but the correct sequence of those instructions as well. Examples of high-level languages used to create e procedure-oriented programs include COBOL, BASIC (Beginner’s All Purpose Symbolic Instruction Code) and C.
Recently, more advanced high-level languages have emerged; these languages are used to create object -oriented programs. Different from procedure perform, an object-oriented program requires the programmer to focus on the objects that the program can use to accomplish its goal. The objects can take n many different forms. For Example Programs wetting for the windows environment typically use objects such as check boxes, list boxes and buttons. A payroll program on the other hand might utilize objects found in the real world. Such as a time cared object an employee objects and check object because each object is viewed as an independent unit and object can be used more than one program, usually with little or more modification. A check object used in a pay roll program. For example also can be used on a sales revenue program ( Which receives checks from customers) and an accounts payable program (Which issues checks to creditors).the ability to use an object for more than one purpose saves programming time and money – and advantage that contributes to the popularity of object – oriented programming. Examples of high level languages used to create object oriented program include Visual basic, java, C++, Visual C++, Visual J# and Visual C #
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