SS3 Second Term Computer Studies Lesson Note – High Level Languages II

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WEEK 6.       

TOPIC: HIGH LEVEL LANGUAGES (HLL)

CONTENT

• Interpreted Language (i) BASIC (ii) Compiled Language PASCAL, COBOL, C, FORTRAN.
• Features of BASIC, C, PASCAL, COBOL.
• Advantages of HLL over ML and LLL.

Sub-topic 1:   Interpreted Language

They are languages that must be read and then executed directed, with no compilation stage. A program called the interpreter is used to read each line of grogram following the program flow, converts it to machine code and it is used to interpret again if the line is executed again.

Compiled Language

Compiled languages are transformed into an executable form before running. They are of two types: (a) machine code generation: some compilers compile source code directly into machine code. This is the original mode of compilation, and languages that are directly and completely transformed to machine-native code in this way may be called ‘truly compiled’ languages e.g. PASCAL. (b) intermediate representation: a language that is compiled to an intermediate representation, is that which can be optimized or saved for later execution without the need to read the source file again. When the intermediate representation is saved it is often represented by a bite-code. The intermediate representation must then be interpreted or further compiled to execute it. E.g. Java.

Advantages of HLL over ML and LLL

1. HLL makes a complex programming simpler, whereas low level languages tend to produce more efficient code.
2. They are considered simply to use due to the numerous technical details, which must be remembered in ML and LLL.
3. Ease of modification and maintenance.
4. Greater portability for a program.

Sub-topic 2:   Features of BASIC

The features of True BASIC included in the above program include:

The first statement is an optional PROGRAM header. The inclusion of a program header is good programming style.

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