Difference Between Assembly Language And High Level Languages
One step removed from the CPU is programming in symbolic form, or assembly language. In assembly language, an operation code is represented by a letter or a series of letters that relates to the operation to be carried out. Thus, R may stand for READ; CLA for CLEAR AND ADD INTO THE ACCUMULATOR; STO for STORE THE CONTENTS OF THE ACCUMULATOR IN MEMORY; and PR for PRINT THE CONTENTS OF A MEMORY LOCATION. The storage locations of the data are also given letter symbols, such as N, M, and K.
The sample assembly-language program in Table I follows the machine-language program in one-to-one order. One assembly-language instruction appears for each machine-language instruction. As a programmer, you are now concerned with symbolic operation codes and symbolic names for the storage locations, which you can devise to relate to the problem.
The CPU does not and cannot execute symbolic programming instructions. The symbolic instructions must be translated or converted into machine language. This is done automatically by the computer, using a program called an assembler. The assembler program is in machine language.
For many people, assembly language is too tedious. Much effort, therefore, has gone into devising higher-level languages that are further removed from the machine.
High-level programming languages enable you to write your instructions more nearly as they would be written in the ordinary context of the problem. Languages for mathematicians permit the writing of formulas. Languages for business emphasize file descriptions of business data and the kind of operations that will keep track of inventories or produce payrolls. Many other languages have also been devised.
Each language is intended to make the work of programming easier. BASIC (for Beginners’ All-purpose Symbolic Instruction Code) was developed in 1965 at Dartmouth College, and is an easy language to learn. Today, programmers can use Visual BASIC to develop applications for Windows, a common software package for PCs. In Visual BASIC, the programmer drags program elements onto a window (or screen) from a toolbox—a collection of preestablished commands that can be used in an application—and writes BASIC for each element. Applications can be created very quickly using Visual BASIC.