Lecture02(constants, variable & data types)

Lecture02(constants, variable & data types)

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  Lecture02(Constants, variable &data types) June 15, 2010 Today's Outline Data Types C Tokens Keywords & Identifiers Constants Variables The four C scopes Type Qualifiers Storage Class Specifiers Md. Mahbub Alam Structured Programming Language 1 (CSE-1121)
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  C Tokens Token: Smallestindividual units in C program are known as token. e.g. Keywords - int, break, for, struct etc Identifiers - count, amount etc Constants - 10, 5.5, -7.5 etc Strings - “DUET”, “1st Year” etc Operators - +, -, *, / Special Symbols - [] {} etc Md. Mahbub Alam Structured Programming Language 2 (CSE-1121)
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  C Data Types All C compiler supports 5 foundational data types, namely integer(int), floating-point(float), double precision floating-point (double), character(char), & void. Data Type Size (bits) char 8 int 16 or 32 float 32 double 64 void type either explicitly declares a function as returning no value or creates generic pointers. Md. Mahbub Alam Structured Programming Language 3 (CSE-1121)
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  C Keywords All keywords have fixed meanings & these meanings can not be changed. Serve as basic building blocks for program statements. All keyword must be written in lowercase letters. • Flow control (6) - if, else, return, switch, case, default • Loops (5) - for, do, while, break, continue • Common types (5) - int, float, double, char, void • Structures (3) - struct, typedef, union • Counting and sizing things (2) - enum, sizeof • Rare but still useful types (7) - extern, signed,unsigned, long, short, static, const • Evil keywords which we avoid (1) - goto • Others (3) - auto, register, volatile Md. Mahbub Alam Structured Programming Language 4 (CSE-1121)
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  C Identifiers InC, the names of variables, functions, labels & various other user- defined items are called identifiers. Rules for identifiers: • First character must be an alphabet or underscore and subsequent characters must be either letter, digits, or underscore. • Only 31 characters are significant. • Can not be the same as a C keywords & should not have the same name as functions that are in C library. • Must not contain white space. Md. Mahbub Alam Structured Programming Language 5 (CSE-1121)
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  Variables Avariable is a named location in memory that is used to hold a value that can be modified by the program. All variable must be declared before they can be used. Format: type varable_name; e.g. int count; Variable name must be meaningful to reflect its function or nature. Variable initializations Format: type variable_name = constant; Where variables to be declared: - Inside function (local variables) - In the definition of function parameters (Formal parameters) - Outside of all functions (global variables) Md. Mahbub Alam Structured Programming Language 6 (CSE-1121)
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  Constants Constantsrefers to fixed values that do not change during program execution. Constants can be of any type of the basic types. Constants are also called literals. int 10, 135, -23 Example: long int 5678349L unisigned int 580U unisigned long int 9845464UL float 120.25f long double 1020.75L character constants ‘D’ string “DUET” HEX 0x80 Octal 016 Md. Mahbub Alam Structured Programming Language 7 (CSE-1121)
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  Backslash Character Constants Backslashcharacter constants are used in output functions. Also known as escape sequence Code Meaning b Backspace n New line f Form feed r Carriage return t Horizontal tab v Vertical tab ” Double quote ’ Single quote Backslash a Alert ? Question mark 0 Null Md. Mahbub Alam Structured Programming Language 8 (CSE-1121)
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  Any Question? Md. MahbubAlam Structured Programming Language 9 (CSE-1121)
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  Thank You All Md.Mahbub Alam Structured Programming Language 10 (CSE-1121)