Introduction to Language Programming Hierarchy of programming lang

Introduction to Language Programming Hierarchy of programming lang. Based on machine independences: 1. Machine language 2. Assembly language 3. Higher level / user oriented language 4. Problem oriented language

Machine level language • Each instruction numeric code • numerical address memory location in computer’s memory • program written in microcode(I. e. microprogram) • microcode a set basic machine instruction

Assembly language • Simbolic version • operation code symbolic code, such ADD, MUL, DIV, PUSH, POP • memory location symbolic name, such PAY, RATE • offerring certain diagnostic and debugging assistance

High level language • Such as FORTRAN, PASCAL, PL/I • offering most of features of an assembly language • offering a more enriched set of language features, such as structured control construct, nested statements, blocks, and procedures

Problem oriented language • Providing for expression of problems in specific app. /problem area. • Such SQL database app, COGO civil eng. App.

Advantages of high level languages over low level such machine and assembly languages • HLL more easier to learn • programmer does’nt to concern with clerical tasks involving numerical or symbolic references to intructions, mem location, constants, etc • programmer is not required to know how to convert data from external forms to various internal forms within the memory of computer • most HLL offer a programmer a variety of control structure, such IF THEN ELSE and CASE statement • programs written in HLL is usually more easily debugged

Advantages > • Availability of certain features such as procedures better documentation • HLL relatively machine independent • since most HLL offer more powerful control and data structuring capability the former class of lang. Facilitates the expression of a solution to particular problem

Translator • Inputing and then converting a source program into object or target program • source program written in a source language and object belongs to object language • assembly assembler machine language • a time at which the conversion of a source program to an object program occurs compile time

Compilation process

Interpretive process

interpreter • interpreter processes an internal form of the source program and data at the same time • interpreter does not generate object code • such BASIC, LISP, SMALLTALK

Model of a compiler • Constructing a compiler very complex • a compiler must perform 2 major task: – analysis of source program front end, the tasks deal with decomposition of source prg into its basic parts – synthesis of corresponding object program back end, the tasks generating and optimizing object program • components of a compiler: – scanner /lexical analyzer separating the incoming text into pieces or tokens – syntax analyzer/parser checking correct tokens and sequences tokens

> models a compiler • Semantic analyzer carrying on semantic analysis, usually connected with intermediate code generator • code optimizer • table symbol

Figure of model of a compiler