Program A computer program (also software, or just a program) is a sequence of instructions written in a sequence to perform a specified task with a computer. 1

An Introduction to Programming with C, Fifth Edition 2 Creating a C Program source code Object code Executable code: exe file created using an IDE

Processing a C Program (cont'd.) C Programming: From Problem Analysis to Program Design, Fifth Edition 3

The Problem Analysis–Coding– Execution Cycle (cont’d.) C++ Programming: From Problem Analysis to Program Design, Fifth Edition 4

Structure of C Program #include void main( ) { printf(“Welcome to Computer Scientists”); getch(); } Program Body main function Starting point of program execution Preprocessor Directives Header File To include header files in our program Contains built-in-functions. These are also called pre-defined or already developed functions File name(standard input output ) h stands for header file Function Name Return type of main function. It is used to determines whether the program is executed successfully or not. Void means nothing Parenthesis shows function. It is used to pass parameters/arguments Body Begin Body End Printtf satns for print funtion. It us used to print the output on the monitor/console. Angle or pointed brackets String or message to be displayed on monitor. It must be enclosed in double quotes(“ “) Each statement must end with semicolon. A statement without semicolon generates syntax error Get character function. It get a character at runtime. But we use it to stay screen to see output 5

Memory Concepts Variable names Correspond to actual locations in computer's memory Every variable has name, type, size and value When new value placed into variable, overwrites previous value 6

Alphabets from A to Z or a to z The digits from 0 to 9 Underscore(_) can be used The first character of an identifier can not be a digit The name of an identifier can not be a reserve word No space allowed in the name of identifier Rules to Declare an Identifier (variable) Valid Name: A Student_Name _Fname Pi Inalid Name: $Sum //special ch. 6StName // 1 st letter digit F name // no space allowed int // reserve word 7 Variable: Location in memory where value can be stored An identifier is a name for a variable, constant, function, etc.

Syntax Data-Type Space Variable-Name(Indentifier); e.g. int frstNumber; char choice; float divide; long output; Identifier (variable) Declaration Data-Type Space Variable-Name(Indentifier) = Value; e.g. int frstNumber=10; char choice=‘y’; float divide=0.0; Syntax Identifier (variable) Initialization 8

Memory Concepts scanf(“%d”,& first); Assume user entered 45 scanf(“%d”,& second); Assume user entered 72 sum = first + second; first 45 first 45 second 72 first 45 second 72 sum 117 Identifier Variable 9

Assignment Operator (=) = (assignment operator) Assigns value to variable Binary operator (two operands) Example: sum = variable1 + variable2; 10

How many bytes I am eating? integer data short2 bytes int2 bytes(16 bit system) 4 bytes (32 bit system) long4 bytes Floating point data float4 bytes double8 bytes long double10 bytes Characterchar 1 byte Booleanbool 1 byte 11

12 Memory Allocation for Arithmetic Data Types Size (bytes)Range of Values Name (alternate)Description AVR GCCMSVC++AVR GCCMSVC++ charCharacter or small integer11 Signed: -128 to 127 (-2 (8-1) to 2 (8-1) -1) Unsigned: 0 to 255 (0 to ) Signed: -128 to 127 Unsigned: 0 to 255 short int (short)Short integer22 Signed: to Unsigned: 0 to Signed: -32,768 to 32,767 Unsigned: 0 to intInteger24 Signed: to Unsigned: 0 to Signed: -2,147,483,648 to 2,147,483,647 Unsigned: 0 to 4,294,967,295 long int (long)Long integer44 Signed: -2,147,483,648 to 2,147,483,647 Unsigned: 0 to 4,294,967,295 Signed: -2,147,483,648 to 2,147,483,647 Unsigned: 0 to 4,294,967,295 long long int (long long)Really long integer88 Signed:  -9.2E+18 to  9.2E+18 Unsigned: 0 to  1.8E+19 Signed:  -9.2E+18 to  9.2E+18 Unsigned: 0 to  1.8E+19 float'Single-precision' floating point number44   1E  38 (7 decimal digits of precision) double'Double-precision' floating point number48   1E  38 (7 decimal digits of precision)   1E  308 (15 decimal digits of precision) long double Long double-precision floating point number8   1E  308 (15 decimal digits of precision)

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Arithmetic Rules of operator precedence Operators in parentheses evaluated first Nested/embedded parentheses  Operators in innermost pair first Multiplication, division, modulus applied next Operators applied from left to right Addition, subtraction applied last Operators applied from left to right 14

Comments Non - executable statements Comments are used for program documentation Two formats Single Line CommentsMulti Lines Comments // This program is used to show the Welcome Message. /* This program is used to show the square of even numbers from 10 to 100. */ 15

Tokens Tokens are individual words and punctuation marks in passage of text. In C++, program the smallest individual units are known as C Tokens. C++ has Six types of Tokens. The Tokens are shown in figure. C++ programs are written using these tokens and the syntax of the language. 16

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C++ keywords Each keyword has a predefined purpose in the language. Do not use keywords as variable and constant names!! Exmples: bool, break, case, char, const, continue, do, default, double, else, extern, false, float, for, if, int, long, namespace, return, short, static, struct, switch, typedef, true, unsigned, void, while etc etc.. 18

19 Thank You New Computer Scientists