Introduction to Programming By : Selam Girma (MSc.) August, 2019 Chapter One Introduction to Programming • Introduction to Programming • Hierarchy of Computer Language • Characteristics of Computer Language • Language Translators 1.1 Introduction to Computer Programming Languages • A computer is a computational device which is used to process the data under the control of a computer program. • Program is an organized sequence of instruction along with data that, when executed, it perform any operation, and do the job it is also known as Code • A program is like a recipe. It contains a list of variables and a list of directions (Statements) that tell the computer what to do, when and how to do it. ✓ The term Instruction is often used to describe the programming Commands 4 Cont . . . Introduction to Computer Programming Lanuage 1.1 Introduction to Computer Programming Languages • These Computer Programs are written in a Programming Language • Programming Languages are an Artificial Language designed to work for different application in different environment. • Programming languages can be used to create programs that controls the behavior of a computer and serve any purpose. • Computer languages have some form of written specification of their :✓ Syntax (Special Rules for organizing program instruction) and ✓ Semantics (Unique set of Keywords, Phrases & Sentences) 5 1.2 Hierarchy of Computer Language • Human Languages are known as natural languages, Unfortunately, computers can not understand natural languages, as a result we must communicate with computers using computer languages. • These languages are :✓ High Level Language ✓ Assembly Language ✓ Machine Language 6 Cont . . . Hierarchy of Computer Language 1.1 Hierarchy of Computer Language Higher Level Languages Lower Level Languages 7 1.2.1 Machine Language • It is the native language of the computer, and it consists of Bits or Binary Digits (1s and 0s) that computer interprets. • Sometimes referred to as Machine Code or Object Code. • It is a system of instructions and data executed by the computer’s CPU. • It is the only language the computer understand without translator. • Machine language instructions typically use some bits to represent operations. • It is difficult to read and write, since it does not resemble conventional mathematical notation or human language, and its codes vary from computer to com 8 1.2.2 Assembly Language • It uses short mnemonic codes (short forms) for instructions & allows programmers to introduce names for blocks of memory to hold data. • It is designed to be easily translated into machine language. • Assembly language programs needed to be “assembled” for execution by the computer. • Each assembly language instruction is translated into one machine language instruction • It requires detailed knowledge of particular internal computer architecture • An assembler is needed to translate the assembly code into machine 9 code. 1.2.3 High Level Language • High Level languages are much closer to human language that enables to write programs which is understandable to programmer (Human). • High level languages are machine independent. • It don’t require programmers to know about internal structure of computer on which High Level Language programs will be executed. • It enables the programmers to write instructions using English words and familiar mathematical symbols and expressions. 10 Advantages of High Level Language over Low Level Language • They are easier to read, write and maintain. • High level languages make complex programming simpler. • High level programming techniques are applicable everywhere computational resources are limited. • Error ratio is less in high level languages and debugging (locate and correct errors in program code) is easier. • Length of the program is also small compared with low level. • Many real time problems can be easily solved with high level language. 11 High Level Vs Low Level Languages 12 1.3 Characteristics of a programming Language • A programming language must be simple, easy to learn and use, have good readability and human recognizable. • Abstraction is a must-have Characteristics for a programming language in which ability to define the complex structure and then its degree of usability comes. • A portable programming language is always preferred. • Programming language’s efficiency must be high so that it can be easily converted into a machine code and executed consumes little space in memory 13 Cont . . . Characteristics of a Programming Language • A programming language should be well structured and documented so that it is suitable for application development. • Necessary tools for development, debugging, testing, maintenance of a program must be provided by a programming language. • A programming language should provide single environment known as Integrated Development Environment(IDE). • A programming language must be consistent in terms of syntax and semantics 14 1.4 Language Translators • Language Translators Convert Programming source code into language that the computer processor understands. • Programming language has many structures but the computer understands only machine language. • Language Translators are of three types:✓ Assembler ✓ Compiler ✓ Interpreter 15 1.4.1 Assembler • Software that translate assembly language program into it equivalent machine language program of computer is called assembler. • It is a Program that takes basic computer instructions & converts them into a pattern of bits (0 & 1) that the computer runs to produce result • The output of the assembler program is called the object code, which is usually a machine code. 16 1.4.2 Compiler • A Compiler is a program that translates a program written in High Level Language into machine language. • Compiler identify the variables used in the instructions and allocate memory. • It also generate error messages, if there are errors in the program. • After every thing is clear, it then compile the program into machine code. • Compiler simply translates the entire source code into executable instructions that a computer can understand, it compiles code and it produce in exe format before it run and is not involved in its execution. 17 Cont . . . Compiler 1.4.2 Compiler • There are two stages of compiler :• Intermediate Compilation ✓ Intermediate level compiles code in the form of Byte Code and save for later execution without the need to re – read the source file. • Machine code compilation. ✓ Machine code compiles source code directly into machine code using Virtual Machines that execute code directly into machine code. 18 Cont . . . Compiler 19 1.4.3 Interpreter • Interpreter is closely related to a compiler, but it can’t create executable file like compiler. • It can convert a source code line – by – line directly into machine code. • It is slower than compiler which translate the entire program into executable machine code. • Every time when the program runs, the interpreter must be present to interpret the source code into machine code.. • Compiler simply translates the entire source program into an object program and is not involved in its execution. 20 Cont . . . Interpreter 21 Thank You! 22
