Lecture 6- Intorduction to C Programming

Lecture 6- Intorduction to C Programming

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  Introduction to CProgramming Md. Imran Hossain Showrov (showrovsworld@gmail.com) 6 1
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  Outline  The CCharacter Set  Identifiers  Keywords  Data Types  Variables  Expressions  Statements  Declarations
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  Objective  This lecturewill cover the basic elements used to construct simple C Statements.These elements include the C character set, identifiers and keywords, data types, constants, variables etc.
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  The C CharacterSet  C uses  The upper case letters (A to Z)  The lower case letters (a to z)  Certain special characters  The Standard requires that an alphabet of 96 symbols is available for C as follows
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  Writing First Programof C Format of main() function
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  Writing First Programof C (cont..) #include <stdio.h> main() { printf(“Welcome to C programmingn”); } Output:
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  Writing First Programof C (cont..)  First line of this program uses # as a compiler directive.  Second line uses a special word main, which denotes the starting point for execution of the program.All programs start their execution from main.  { refers start and } refers end of the main.  printf is an output statement used to display any message on the screen.  n represents new line.
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  Identifiers  Identifiers arenames that are given to various program elements such as variables, functions and arrays.  Identifiers consists of letters, digits and underscore character (_), in any order, But the first character must be a letter.
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  Identifiers (cont..)  Thefollowing names are valid identifiers: x y12 sun_1 _temperature names area tax_rate TABLE  The following names are not valid identifiers: 4th The first character must be a letter “x” Illegal characters (“) order-no Illegal character (-) error flag Illegal character (blank space)
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  Keywords  Keywords arereserve words that have standard, predefined meaning un C.  It can only be used for their intended purpose.  It cannot be used as programmer-defined identifiers.
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  Keywords (cont..)
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  Data Types  Datatypes are declarations for memory locations or variables that determine the characteristics of the data that may be stored and the methods (operations) of processing that are permitted involving them.  C supports several data types
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  Data Types (cont..) DataType Description Example int integer quantity 12, 96 etc. char single character A, b, 0 etc. float floating-point number 12.666428 double double- precision floating point number 12.6664287277 62776
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  Variables  A variableis an identifier that is used to represent some specific type of information within the designated portion of the program.  Example: – int a, b, c; – char d; – a = 3; – b= 5; – c = a + b;
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  Expressions  An expressionrepresents a single data item, such as a number or a character.  The expression may consist of a single entry, such as a constant.  Expression can also represent logical conditions that are either true or false.  Example: ● a + b ● x = y ● x <= y ● x == y ● c = a + b ● ++i
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  Statements  A statementcauses the computer to carry out some action.  There are three different classes of statements in C 1. Expression statement 2. Compound statement 3. Control statement  Example: a = 3; c = a + b; ++i;
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  Declarations  A declarationassociates a group of variables with a specific data types.  All variables must be declared before they can appear in executable statements.  A declaration of a data type, followed by one or more variable names, ending with semicolon.  Example:  int a, b, c;  float root1, root2;  char flag, text[80];
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  Example 1 #include<stdio.h> main() { int sum,a =10, b = 20; sum = a+b; printf(“%dn”, sum); }
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  Example 1 (cont..) Insidethe main function:  Identifiers:  Here, sum, a, b is an identifier.  Keywords:  Here, int is a keyword  Data Type:  Data type of sum, a, b is int  Variable:  Here, sum, a, b are variables.  Expression:  sum = a + b ;