03 Es26 Lab - Intro To C

Introduction to C Programming

3

Introduction to Programming

Objectives After completing this lesson, you should be able to do the following: • Explain the process of program development • Identify and describe the basic program structure • Encode, compile and run simple computer programs

Introduction to Programming

Introduction to Programming • Programs are developed to instruct computers to do specific tasks, or solve specific problems • A finite set of instructions that if followed accomplishes a particular task is called an algorithm • Thus, programming is the activity of communicating algorithms to computers Introduction to Programming

Program Development Process Problem or Task check it

make list

Requirements List design algorithm

verify

Algorithm verify

code program

Program test and debug

Introduction to Programming

Typical Programming Environment Program is encoded in a text editor and stored on a disk

Editor

Object code is created by a compiler and stored on a disk

Compiler

Executable code is created by the linker by linking the object codes and stored on disk

Linker

Source code

Object file

Disk

Executable file

Introduction to Programming

Typical Programming Environment Loader places the executable program in memory

Loader

CPU

Disk

CPU fetches each instruction from memory, executes it, and possibly stores new data as the program executes

Introduction to Programming

Primary memory

Typical Programming Environment In A Nutshell Edit

Compile

Execute

source code

object code

executable code

Introduction to Programming

The C Programming Language • We will be learning programming using the C programming language • C was developed by Dennis Ritchie between 1969 and 1973 at the AT&T Bell Labs • C was designed for systems programming • C is considered as a generalpurpose programming language Introduction to Programming

History of C Basic Common Programming Language (BCPL) (Martin Richards)

B (Ken Thompson)

C (Dennis Ritchie)

Introduction to Programming

ANSI C • There are different C compilers developed over the years such as Turbo C, Object-C and Windows C • The American National Standards Institute (ANSI) adopted the ANSI standard for C (ANSI C) in 1990 • C is widely used today because of its rich standard library of functions

Introduction to Programming

Sample C Program 1: Hello World Source code: hello.c /* This program will display “Hello World” */ #include <stdio.h> int main() { printf(“Hello World!”); return 0; }

Output Hello World! Introduction to Programming

C Program Structure preprocessor directives main function heading { statements }

Introduction to Programming

Preprocessor Directives • Preprocessor directives are commands that give instructions to the C preprocessor • Its job is to modify the text of a C program before it is compiled • It begins with a number symbol (#) as its first non-blank character • Example: #include #define

Introduction to Programming

Preprocessor Directive: #include source code

source code

Preprocessor File to be included

File to be included Resulting file

Introduction to Programming

Header Files • A header file is a collection of useful functions and symbols that may be accessed by a program • Its file name ends with a .h extension • Example: #include <stdio.h> #include <string.h>

Introduction to Programming

FILE NULL

EOF output

input

STDIO.H

Main Function • Every C program has a main function • Marks the beginning of the main function where program execution begins • Basic form: main( ) { main function body } Introduction to Programming

Program Statements • Program statements are elementary components of a program

Introduction to Programming

Comments • Comments are used to add remarks to a program • Any number of comments can be placed anywhere in the program without affecting its content and speed • The compiler simply ignores them and treats them as white spaces • In C, comments are delimited by the following pairs of characters /* and */ /* This is a comment */ /* Name: Juan de la Cruz * * Student Number: 96-00000 * * Course: BS Computer Science */ Introduction to Programming

Comments ... printf( “ /* This is NOT a comment */ ” ); ...

• Strings inside quotes are displayed as it is

Introduction to Programming

Sample C Program 2: Average of Two Numbers /* Filename: average.c */ #include <stdio.h> int main(void) { float num1, num2, average; printf(“Enter the first number: “); scanf(“%f”,&num1); printf(“Enter the second number: “); scanf(“%f”,&num2); average = (num1 + num2)/ 2.0; printf(“The average of %f and %f is %f”,num1,num2,average); return 0; } Introduction to Programming

Laboratory Exercise Overview • Become familiar with the C programming environment • Learn how to encode, compile and run simple C programs

Introduction to Programming