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Unit   ii Unit ii Presentation Transcript

  • UNIT 2 C PROGRAMMING BASICS
  • What is C? • Language written by Brian Kernighan and Dennis Ritchie • C has been used as a general – purpose language because of its popularity • It was written to become first “portable” language
  • Why use C? • Mainly because it produces code that runs nearly as fast as code written in assembly language. Some examples of the use of C might be: • Operating Systems • Language Compilers • Assemblers • Text Editors • Print Spoolers • Network Drivers • Modern Programs • Data Bases • Language Interpreters • Utilities Mainly because of the portability that writing standard C programs can offer
  • History • 1960 : - • ALGOL was found by International group of computer users. • COBOL was found for commercial application usage. • FORTRAN was found for scientific applications. • In 1967: - • Basic Combined Programming Language (BCPL) • developed by Martin Richards at Cambridge University. • a single language which can program all possible applications, • In 1970: - • a language called B was developed by Ken Thompson at AT & T’s Bell Labs.
  • History • In 1972: - • Dennis Ritchie at Bell Labs developed a language with some additional features of BPCL and B called C. • In 1978: - • Publication of The C Programming Language by Kernighan & Ritchie caused a revolution in the computing world. • In 1983: - • the American National Standards Institute (ANSI) established a committee to provide a modern, comprehensive definition of C. The resulting definition, the ANSI standard, or "ANSI C", was completed late 1988.
  • Why C Still Useful? • C characteristics:  Highly structured language  Handle bit-level operations  Machine independent language-highly portable  Supports variety of data types and powerful set of operators  Supports dynamic memory management by using concept of pointers • C is used to develope:  System software - Compilers, Editors, embedded systems  data compression, graphics and computational geometry, utility programs  databases, operating systems, device drivers, system level routines  there are zillions of lines of C legacy code  Also used in application programs
  • Programming languages • Some understandable directly by computers • Others require “translation” steps • Various programming languages • Machine language • Assembly language • High-level language • Machine language • Natural language of a particular computer • Consists of strings of numbers(1s, 0s) • Instruct computer to perform elementary operations one at a time • Machine dependent
  • Programming languages • Assembly Language • English like abbreviations • Assemblers: • Translators of programs • Convert assembly language programs to machine language. • E.g. add overtime to base pay and store result in gross pay LOAD BASEPAY ADD OVERPAY STORE GROSSPAY
  • Programming languages • High-level languages • To speed up the programming process • Single statements for accomplishing substantial tasks • Compilers - convert high-level programs into machine language • E.g. add overtime to base pay and store result in gross pay grossPay = basePay + overtimePay
  • Basics of C Environment • C systems consist of 3 parts • Environment • Language • C Standard Library • Development environment has 6 phases  Edit - Writing the source code by using some IDE or editor  Pre-processor - Already available routines  Compile - translates or converts source to object code for a specific platform ie., source code -> object code  Link - resolves external references and produces the executable module  Load – put the program into the memory  Execute – runs the program
  • Basics of C Environment Editor DiskPhase 1 Program edited in Editor and stored on disk Preprocessor DiskPhase 2 Preprocessor program processes the code Compiler DiskPhase 3 Creates object code and stores on disk Linker DiskPhase 4 Links object code with libraries and stores on disk
  • Basics of C Environment LoaderPhase 5 Puts program in memory Primary memory CPUPhase 6 Takes each instruction and executes it storing new data values Primary memory
  • Executing a C Program Steps involved in execution are • Creating the program • Compiling the program • Linking the program with functions that are needed from the C library • Executing the program
  • Executing a C Program Edit Program Source Code Compile Object Code Link Object Code Executable Library Files
  • Basics Structure of C Program Documentation section Link section Definition section Global declaration section main() function section { Declaration part Executable part } Subprogram section (user defined function)
  • Simple C Program /* A first C Program*/ #include <stdio.h> void main() { printf("Hello World n"); }
  • Simple C Program • Line 1: #include <stdio.h> • As part of compilation, the C compiler runs a program called the C preprocessor. The preprocessor is able to add and remove code from your source file. • In this case, the directive #include tells the preprocessor to include code from the file stdio.h. • This file contains declarations for functions that the program needs to use. A declaration for the print function is in this file.
  • Simple C Program • Line 2: void main() • This statement declares the main function. • C program can contain many functions but must always have one main function. • A function is a self-contained module of code that can accomplish some task. • Functions are examined later. • "void" specifies the return type of main. In this case, nothing is returned to the operating system.
  • Simple C Program • Line 3: { • This opening bracket denotes the start of the program.
  • Simple C Program • Line 4: printf("Hello Worldn"); • printf is a function from a standard C library that is used to print strings to the standard output, normally your screen. • The "n" is a special format modifier that tells the printf to put a line feed at the end of the line. • If there were another printf in this program, its string would print on the next line.
  • Simple C Program • Line 5: } • This closing bracket denotes the end of the program.
  • C Character Set • Characters are the basic building blocks in C program, equivalent to ‘letters’ in English language • Characters can be used to form words, numbers and expressions • Characters in C are grouped into following categories • Letters ex:a…z,A…Z • Digits ex:0…9 • Special characters ex:,,&,@,_,+,-,….. • White spaces ex:blank space horizontal tab new line…….
  • C Tokens • In a passage of text, individual words and punctuation marks are called tokens • In a C source program, the basic element recognized by the compiler is the "token." • C Tokens are  Keywords - int, float, while  Identifiers - sum, main  Constants - 100, -55.5  Strings - “ABC”, “Hello”  Operators - +, -, *, /, ++  Special symbols - {, },[, ]
  • Keywords • All keywords are reserved words have fixed meanings and these meanings cannot be changed • Have special meaning to the compiler, cannot be used as identifiers in our program. • Keywords serve as basic building blocks for program statement • Keywords must be written in lowercase • Displayed in BLUE color in MS Visual C++
  • Some Keywords Keywords auto double int struct break else long switch case enum register typedef char extern return union const float short unsigned continue for signed void default goto sizeof volatile do if static while
  • Identifiers • Refer to the names of variables, functions and arrays • User defined names and consist of a letters and digits, with a letter as a first character Rules for Identifiers • First character must be an alphabet • Must consist of only letters, digits and underscore • Only first 32 characters are significant • Cannot use a keyword • Must not contain white space • Case sensitive-Identifier Sub differ from sub
  • Identifiers Examples of legal identifier: Student_age, Item10, counter, number_of_character Examples of illegal identifier Student age (embedded blank) continue (continue is a reserved word) 10thItem (the first character is a digit) Principal+interest (contain operator character +)
  • 1. Avoid excessively short and cryptic names such as x or wt. Instead, use a more readable and descriptive names such as student_major and down_payment. 2. Use underscores or capital letters to separate words in identifiers that consist of two or more words. Example, student_major or studentMajor are much easier to read than studentmajor. Recommendations forConstructingIdentifiers
  • Constants • Constants refers to fixed values that do not change during the execution a program Types of Constants Numeric Constants  Integer Constants - 234, 045, 0x2A, 0X3B  Real Constants - 2.345, 0.64e-2 Character Constants  Single Character Constants ‘5’, ‘A’  String Constants “Hello”
  • IntegerConstant Positive or negative whole numbers with no fractional part Optional + or – sign before the digit. It can be decimal (base 10), octal (base 8) or hexadecimal (base 16) Hexadecimal is very useful when dealing with binary numbers Example: const int MAX_NUM = 10; const int MIN_NUM = -90; const int Hexadecimal_Number = 0xf87;
  • RulesforDecimalIntegerConstant 1. Decimal integer constants must begin with a nonzero decimal digit, the only exception being 0, and can contain decimal digital values of 0 through 9. An integer that begins with 0 is considered an octal constant 2. If the sign is missing in an integer constant, the computer assumes a positive value. 3. Commas are not allowed in integer constants. Therefore, 1,500 is illegal; it should be 1500. Example of legal integer constants are –15, 0, +250 and 7550 Example of illegal constants 0179 is illegal since the first digit is zero 1F8 is illegal since it contains letter ‘F’ 1,700 is illegal since it contains comma
  • FloatingPointConstant • Positive or negative decimal numbers with an integer part(optional), a decimal point, and a fractional part (optional) Example 2.0, 2., 0.2, .2, 0., 0.0, .0 • It can be written in conventional or scientific way • 20.35 is equivalent to 0.2035E+2 (0.2035 x 102 ) • 0.0023 is equivalent to 0.23e-2 (0.23 x 10-2) • E or e stand for “exponent” • In scientific notation, the decimal point may be omitted. Example: -8.0 can rewritten as -8e0
  • Floating Point Constant • C support 3 type of Floating-point: float (4 bytes), double (8 bytes), long double (16 bytes) • By default, a constant is assumed of type double • Suffix f(F) or l(L) is used to specify float and long double respectively Example: const float balance = 0.125f; const float interest = 6.8e-2F const long double PI = 3.1412L; const long double planet_distance = 2.1632E+30l
  • • A character enclosed in a single quotation mark • Example: • const char letter = ‘n’; • const char number = ‘1’; • printf(“%c”, ‘S’); • Output would be: S How to write a single quotation mark? ‘’’ is ambiguous, so escape character – back slash Example: ‘’’ Character Constants
  • String Literals • A sequence of any number of characters surrounded by double quotation marks. • Example: • “Human Revolution” • How to write special double quotation mark? • “”” is ambiguous, so use escape character • Example: printf(“He shouted, “Run!””); output: He shouted, “Run!” - The escape character along with any character that follow it is called Escape Sequence
  • BackslashCharacter Constants Escape Sequence Name Meaning a Alert Sounds a beep b Back space Backs up 1 character f Form feed Starts a new screen of page n New line Moves to beginning of next line r Carriage return Moves to beginning of current line t Horizontal tab Moves to next tab position v Vertical tab Moves down a fixed amount Back slash Prints a back slash ’ Single quotation Prints a single quotation ” Double quotation Prints a double quotation ? Question mark Prints a question mark
  • Backslash Character Example Program #include<stdio.h> void main() { printf("nabc"); printf("rdef"); printf("bghin"); printf("HaitHello"); } Output deghi Hai Hello
  • Variables • A variable is a data name used for storing a data value • The value may be changed during program execution Rules for defining variables • Must begin with a character • Should not be a C keyword • May be combination of lower and upper characters • Should not start with a digit • Maximum characters upto 31 characters Example Sum, avg_wt, item
  • Declaration of Variables • Syntax for declaring a variable is as follows data-type v1,v2,….vn; Example int i,j,sum; float avg; double ratio; unsigned int fact;
  • DATATYPE • Datatype is the most important attributes of an identifier. It detemines the possible values. • Classification of Datatypes -Basic Datatypes -Derived datatypes -User-defined datatypes Basic/Primitive Datatypes: Character (char) Integer (int) Single-precision floating point (float) Double-precision floating point (double) No value available (void) Derived Datatypes: Array type (char[], int[]) Pointer type (char*, int*) Functiontype (int(int,int), float(int))
  • • User-defined datatypes It provides flexibility to the user to create new datatypes. Newly created called User-defined datatypes. Structure Union Enumeration Syntax: data_type variable_name Example: int age; char ch; float avg; int a,b,c;
  • Data Types Initializing Variables • Variables declared can be assigned or initialized using an assignment operator ‘=‘ Syntax: variable_name=constant; or data_type variable_name=constant; Example: int age; char ch=‘A’; age=10; float avg=10.5;
  • Data Types in C Type Keyword Byte s Range character char 1 -128...127 integer int 2 -32768...32767 short integer short 2 -32768...32767 long integer long 4 -2,147,483,648...2,147,438,647 long long integer long long 8 -9223372036854775808 … 9223372036854775807 unsigned character unsigned char 1 0...255 unsigned integer unsigned int 2 0...4,294,967,295 unsigned short integer unsigned short 2 0...65535 unsigned long integer unsigned long 4 0...4,294,967,295 single-precision float 4 1.2E-38...3.4E38 double- precision double 8 2.2E-308...1.8E308
  • Expressions • Operands It specifies an entity on which an operation is to be performed. It may be a variable name, a constant, a function call or a macro name eg: a=printf(“Hello”)+2 • Operators It specifies the operation to be applied to its operands.
  • SimpleExpressionand Compound Expression • An Expression has only one operator called Simple expression eg: a+2 • An Expression has more than one operator called Compound Expression. eg: b=2+3*5
  • Properties Of Operators • Precedence • Associativity Precedence: • Priority allotted to the operator • Each operator in C has a precedence associated with it. • In compound expression, if the operator involved different precedence, the operator of highest precedence operates first. Ex: 8+9*2-10 =8+18-10 =26-10 =16
  • Associativity: • Expression having operators with equal precedence • associativity property decides which operation is performed first • In compound expression, when several operators of the same precedence appear together, the operators are evaluated according to their associativity. Types: Left to Right Right to left 12*4/8%2 x=8+5%2 = 48/8%2 =8+1 = 6%2 =9 = 0
  • • Operators has same precedence- same associativity • If operators are left-to-right, applied in a left-to-right order • If operators are right-to-left, applied in a right-to-left order • Multiplication and division operators are left-to-right associative
  • Operators • An operator is a symbol that tells the computer to perform certain mathematical or logical manipulations Classification of Operators: Number of operands on which an operator operates The role of an operator Classification based on Number of operands • Unary- it operates on only one operand Eg: &, sizeof operator, !, ~, ++, -- • Binary – it operates on two operands eg: *, /, <<, ==,&&, & • Ternary- it operates on three operands eg: ?:
  • Classification based on Role of Operator Arithmetic Operators +, -, *, /, % Relational Operators <, <=, >, >=, ==, != Logical Operators &&, ||, ! Assignment Operators = Increment and Decrement Operators ++,-- Conditional Operators ?= Bitwise Operators &,|, ^, <<, >> Special Operators ,, sizeof, &, * ., ->
  • Arithmetic Operators C Operation Algebraic C Addition (+) f + 7 f + 7 Subtraction (-) p – c p – c Multiplication (*) bm b * c Division (/) x / y x / y Modulus (%) r mod s r % s
  • Arithmetic Operators Example Program #include <stdio.h> #include <conio.h> void main() { int x,y, a,s,m,d,r; clrscr(); printf(“Enter two numbers:”); scanf(“%d%d”,&x,&y); a = x + y; printf(“a = %dn",a); s = x - y; printf(“s = %dn",s); m = x * y; printf(“m = %dn",m); d = x / y; printf(“d = %dn",d); r = x % y; printf("r = %dn",r); } Output Enter two numbers:10 20 a = 30 s = -10 m = 200 d = 0 r = 10
  • Binary Arithmetic operators • It is used in 3 different modes Integer mode
  • Relational Operators • Greater than > • Less than < • Greater than or equal to >= • Less than or equal to <= • Equal to == • Not equal to != Condition true return 1 Condition false return 0
  • Relational Operators Example Program #include<stdio.h> #include<conio.h> void main() { int x,y,r; clrscr(); printf(“Enter 2 nos. x & y:”); scanf(“%d%d”,&x,&y); r=(x==y); printf("%dn",r); r=(x!=y); printf("%dn",r); r=(x>y); printf("%dn",r); r=(x>=y); printf("%dn",r); r=(x<y); printf("%dn",r); r=(x<=y); printf("%dn",r); } Output Enter 2 nos. x & y: 10 20 0 1 0 0 1 1
  • Logical Operators Operator Example Meaning && (Logical AND) (Condition1) && (Condition2) Both conditions should satisfy to proceed || (Logical OR) (Condition1) || (Condition2) Either one condition satisfied proceed to next operation ! (Logical NOT) !(Condition1) The condition not satisfied proceed to next operation
  • Logical Operators Example if ((x>20) && (x<100)) printf("x is inside open interval 20- 100"); if ((x<5) || (x>20)) printf("x is not inside closed interval 5-20"); if (!(x>20)) printf("x is smaller or equal to 20");
  • Logical Operators Example //Greatest of 3 numbers using logical operators #include<stdio.h> #include<conio.h> void main() { int x,y,z; clrscr(); printf(“Enter 3 nos. x ,y,z:”); scanf(“%d%d%d”,&x,&y,&z); if((x>y)&&(x>z)) printf(“x is greatest”); if((y>x)&&(y>z)) printf(“y is greatest”); if((z>x)&&(z>y)) printf(“z is greatest”); } Output Enter 3 nos. x ,y,z: 40 20 30 x is greatest Enter 3 nos. x ,y,z: 10 40 30 y is greatest Enter 3 nos. x ,y,z: 10 20 30 z is greatest
  • Assignment operators Operator Example Meaning = a = b a = b + = a + = b a = a + b - = a - = b a = a – b * = a * = b a = a * b / = a / = b a = a / b % = a % = b a = a % b
  • Increment/Decrement operators Operator Example Meaning ++ a++ First does the operation and increments the value + + ++a First Increments the value and does the operation -- a-- First does the operation and decrements the value -- --a First decrements the value and does the operation
  • Increment/Decrement operators Program void main() { int c; c = 5; printf(“%dn”, c); printf(“%dn”, c++); printf(“%dnn”, c); c = 5; printf(“%dn”, c); printf(“%dn”, ++c); printf(“%dn”, c); } Output 5 5 6 5 6 6 c=10 x=c++ + ++c; x=? C=?
  • Conditional Operator Conditional Operator (?:) is ternary operator (demands 3 operands), and is used in certain situations, replacing if-else condition phrases. Conditional operator’s syntax is: condition?expression1:expression2; If condition is true, expression1 is executed. If condition is false, expression2 is executed. Example: int a, b, c; ... c = a > b ? a : b; // if a>b "execute" a, else b and assign the value to c
  • Bitwise Operators Operator Meaning & Bitwise AND | Bitwise OR ^ Bitwise XOR ~ One‟s Complement << Left Shift >> Right Shift
  • Bitwise Operators Example Let A=0x56 and B=0x32 A & B ( Bitwise AND ) 0 1 0 1 0 1 1 0 0 0 1 1 0 0 1 0 --------------------- 0 0 0 1 0 0 1 0 --------------------- A ^ B ( Bitwise XOR ) 0 1 0 1 0 1 1 0 0 0 1 1 0 0 1 0 --------------------- 0 1 1 0 0 10 0 --------------------- A | B ( Bitwise OR ) 0 1 0 1 0 1 1 0 0 0 1 1 0 0 1 0 --------------------- 0 1 1 1 0 1 1 0 --------------------- ~ A ( Complement ) 0 1 0 1 0 1 1 0 --------------------- 1 0 1 0 1 0 0 1 ---------------------
  • Bitwise Operators Example Let A=0x56 A << 2 ( Left Shift ) 0 1 0 1 0 1 1 0 << 2  0 1 0 1 0 1 1 0 0 0 ( 0x158 ) A >> 2 ( Right Shift ) 0 1 0 1 0 1 1 0 >> 1  0 1 0 1 0 1 1 ( 0x2B) NOTE: For multiply given number by two, left shifted by one time, i.e., a<<1 For divide given number by two, right shifted by one time, i.e., a>>1
  • Bitwise Operators Example Write a program to shift inputed data by three bits left and right Program void main() { int x,y; clrscr(); printf(“Enter value of x:”); scanf(“%d”,&x); y=x<<3; printf(“Left shifted data=%d”,y); printf(“Right shifted data=%d”,x>>3); } Output: Enter value of x:16 Left shifted data=128 Right shifted data=2
  • Special Operators • C supports some special operators such as comma operator, size of operator, pointer operators (& and *) and member selection operators (. and ->). • The size of and the comma operators are discussed here. The remaining operators will see in pointer chapter Comma Operator • The comma operator can be used to link related expressions together. A comma-linked list of expressions are evaluated left to right and value of right most expression is the value of the combined expression. Example value = (x = 10, y = 5, x + y); for (n=1, m=10, n <=m; n++,m++) t = x, x = y, y = t;
  • Special Operators Sizeof Operator • The operator sizeof gives the size of the data type or variable in terms of bytes occupied in the memory. The operand may be a variable, a constant or a data type qualifier. • The size of operator is normally used to determine the lengths of arrays and structures when their sizes are not known to the programmer. It is also used to allocate memory space dynamically to variables during the execution of the program. Example int sum; m = sizeof(sum);  2 n = sizeof(long int);  4 k = sizeof(235L);  4
  • Expressions Arithmetic Expressions • An expression is a combination of variables constants and operators written according to the syntax of C language. Algebraic Expression C Expression a x b – c a * b – c (m + n) (x + y) (m + n) * (x + y) 3x2 +2x + 1 3*x*x+2*x+1
  • Expressions Evaluation of Expressions • Expressions are evaluated using an assignment statement of the form Variable = expression; Variable is any valid C variable name. The expression is evaluated first and then replaces the previous value of the variable on the left hand side. All variables used in the expression must be assigned values before evaluation is attempted. Example x = a * b – c y = b / c * a z = a – b / c + d;
  • Decision Making - Branching • Decision making statements are used to skip or to execute a group of statements based on the result of some condition. • The decision making statements are, − simple if statement − if…else statement − nested if − else … if ladder − switch statement − goto • These statements are also called branching statements
  • Simple if statement Syntax: if(condition) { Statements; } if(condition) Statements; False True (Bypass)
  • Simple if - Example # include <stdio.h> void main () { int number; printf("Type a number:"); scanf("%d",&number); if (number < 0) number = -number; printf ("The absolute value is %d",number); } Output Type a number -50 The absolute value is 50
  • if - else statement Syntax: if(condition) { True block statements; } else { False block statements; } if(condi tion) True Block Statement False True False Block Statements
  • if – else Example # include <stdio.h> void main () { int num; printf ("Type a number:"); scanf ("%d", &num); if (number < 0) printf(“The number is negative”); else printf(“The number is positive”); } Output Type a number 50 The number is positive
  • if – else Example #include<stdio.h> void main() { Int num; printf ("Enter a number:"); scanf ("%d",&num); if (num%2==0) printf ("The number is EVEN.n"); else printf ("The number is ODD.n"); } Output Enter a number 125 The number is ODD
  • Nested if Statement • if statement may itself can contain another if statement is known as nested if statement. Syntax: if(condition1) { if(condition2) { True block statement of condition1 & 2; } else { False block statement of condition2; } } else { False block statements of condition1; }
  • Nested if Statement condition1 True Block Statements of condition 1 & 2; False True False Block Statements of condition 1; if(condition2) True False Block Statements of condition 2; False
  • Nested if Example # include <stdio.h> void main() { int n1,n2,n3,big; printf (“Enter 3 numbers:"); scanf ("%d %d %d", &n1,&n2,&n3); if (n1 > n2) { if(n1 > n3) big = n1; else big = n3; } if(n2 > n3) big = n2; else big = n3; printf(“The largest number is: %d”,big); } Output Enter 3 numbers:10 25 20 The largest number is: 25
  • Else - if Ladder Statement Syntax if (condition1) statement block 1; else if (condition2) statement block 2; else if (condition3) statement block 3; : : else if (condition) statement block n; else default statement;
  • Else - if Ladder Statement If(condition1) Default Statements; True False Statements1; Else if(condition2) True Statements2; False Else if(condition3) Statements3; False True
  • Else - if Ladder Example #include <stdio.h> void main () { int mark; printf ("Enter mark:"); scanf ("%d", &mark); if (mark <= 100 && mark >= 70) printf ("n Distinction"); else if (mark >= 60) printf("n First class"); else if (mark >= 50) printf ("n Second class"); else printf ("Fail"); } Output Enter mark: 75 Distinction
  • Switch Statement Syntax switch ( expression ) { case value1: program statement; ...... break; case value2: program statement; ....... break; ……. ……. case valuen: program statement; ....... break; default: program statement; ....... break; }
  • Switch Statement Switch (Expression) Case 1 Statements Case 2 Statements Case 3 Statements Case 4 Statements
  • Switch Statement Example #include <stdio.h> void main () { int num1, num2, result; char operator; printf ("Enter two numbers:"); scanf ("%d %d", &num1, &num2); printf ("Enter an operator:"); scanf ("%c", &operator); switch (operator) { case '+': result = num1 + num2; break; case '-': result = num1 - num2; break; case '*': result = num1 * num2; break; case '/': if (num2 != 0) result = num1 / num2; break; default: printf ("n unknown operator"); break; } printf (“Result=%d", result); } Output Enter two numbers:10 20 Enter an operator:+ Result=30
  • Switch Statement Example #include<stdio.h> #include<conio.h> #include<string.h> void main() { char st[100]; int i,count=0; clrscr(); printf("Enter line of text:"); gets(st); for(i=0;st[i]!='0';i++) { switch(st[i]) { case 'a': count++; break; case 'e': count++; break; case 'i': count++; break; case 'o': count++; break; case 'u': count++; break; } } printf("n Number of vowels: %d",count); getch(); } Output Enter line of text: Hello World Number of vowels: 3
  • goto statement •The goto statement used to transfer the program control unconditionally from one statement to another statement. •The general usage is as follows: goto label; Label: ………… ………… .............. ………… ………… ………… ………… ………… Label: Statement; goto label; ………… •The goto requires a label in order to identify the place where the branch is to be made. •A label is a valid variable name followed by a colon.
  • goto statement example #include <stdio.h> void main () { int n, sum = 0, i = 0; printf ("Enter a number:"); scanf ("%d", &n); inc: i++; sum += i; if (i < n) goto inc; printf ("n 1+2+3+…+%d = %d",n,sum) } Output Enter a number:5 1+2+3+…+5=15
  • Looping statements • The test may be either to determine whether the i has repeated the specified number of times or to determine whether the particular condition has been met. • Type of Looping Statements are • while statement • do-while statement • for statement
  • while statement Syntax while (test condition) { body of the loop; } While (test condition) Body of the i; False True
  • while statement example #include<stdio.h> void main() { int n,x,sum=0; printf("Enter a number: "); scanf("%d",&n); while(n>0) { x=n%10; sum=sum+x; n=n/10; } printf("Sum of digits of a number=%d",sum); } Output Enter a number: 275 Sum of digits of a number=14
  • while statement example #include<stdio.h> void main() { int num,r,sum=0,temp; printf("Enter a number: "); scanf("%d",&num); temp=num; while(num!=0) { r=num%10; sum=sum+(r*r*r); num=num/10; } if(sum==temp) printf("%d is an Armstrong number“ ,temp); else printf("%d is not an Armstrong number“ ,temp); } Output Enter a number: 275 275 is an Armstrong number Enter a number: 153 153 is an Armstrong number
  • do..while statement • Since the body of the i is executed first and then the i condition is checked we can be assured that the body of the i is executed at least once. Syntax do { body of the loop; } while (test condition);
  • do..while statement While (test condition) Body of the loop False True do
  • do..while statement example #include<stdio.h> void main() { int num=0, rev_num=0; printf(“Enter the number:”); scanf(“%d”,&num); do { ld=num%10; rev_num=rev_num*10+ld; num=num/10; } while(num>0); printf(“nReversed number is %d”,rev_num); } Output Enter the number:275 Reversed number is 572
  • while and do..while comparison While Do…while 1) Syntax: while(condition) { Body of the loop } 1) Syntax: do { Body of the loop }while(condition); 2) This is decision making and looping statement 2) This is also -decision making and looping statement 3) This is the top tested loop 3) This is the bottom tested loop 4)Loop will not be executed if the condition is false in first check 4) Loop will be executed atleast once even though the condition is false in first check
  • for statement ■ The for loop is most commonly and popularly used looping statement in C. The for loop allows us to specify three things about the loop control variable i in a single line. They are, ■ Initializing the value for the i ■ Condition in the i counter to determine whether the loop should continue or not ■ Incrementing or decrementing the value of i counter each time the program segment has been executed. Syntax for(initialization; test condition;increment/decrement) { body of the loop; }
  • for statement test condition Initialization; False True Increment/Decrement; Body of the loop
  • for statement example // Number 1 to 10 divisible by 2 but not divisible by 3 and 5 #include<stdio.h> void main() { int i; for(i=1;i<=10;i++) { if(i%2==0&&i%3!=0&&i%5!=0) printf("%dn",i); } } Output 2 4 8
  • for statement example //12+22+32+…. n2 #include<stdio.h> //<math.h> void main() { int n, i,sum=0; printf(“Enter the number:”); scanf(“%d”, &n); for(i=1;i <= n;i++) { sum = sum + i*i; //pow(i,2) } printf(“Sum of series=%d”,sum); } Output Enter the number:5 Sum of series=55
  • break statement ■ Sometimes while executing a loop it becomes desirable to skip a part of the loop or quit the loop as soon as certain condition occurs. ■ For example consider searching a particular number in a set of 100 numbers. As soon as the search number is found it is desirable to terminate the loop. ■ C language permits a jump from one statement to another within a loop as well as to jump out of the loop. ■ The break statement allows us to accomplish this task. A break statement provides an early exit from for, while, do and switch constructs. ■ A break causes the innermost enclosing loop or switch to be exited immediately.
  • break statement #include<stdio.h> void main() { int mark, i=0,sum=0; float avg; printf(“Enter the marks, -1 to end:”); while(1) { scanf(“%d”, &mark); if(mark == -1) break; sum+=mark; i++; } avg=(float)sum/i; printf(“nThe average marks is: %f”, avg); } Output Enter the marks, -1 to end: 55 22 11 66 -1 The average marks is:38.500000
  • continue statement ■During loop operations it may be necessary to skip a part of the body of the loop under certain conditions. ■Like the break statement C supports similar statement called continue statement. ■The continue statement causes the loop to be continued with the next iteration after skipping any statement in between.
  • continue statement #include < stdio.h > void main() { int i, num, sum=0; printf(“Enter the integer:”); for (i = 0; i < 5; i++) { scanf(“%d”, &num); if(num < 0) { printf(“You have entered a negative numbern”); continue; } sum+=num; } printf(“Sum of positive numbers entered = %d”,sum); } Output Enter the integer:11 22 33 -1 You have entered a negative number 44 Sum of positive numbers entered =110
  • break and continue comparison Break Continue 1) Syntax: break; 1) Syntax: continue; 2) Takes the control to outside of the loop 2) Takes the control to beginning of the loop 3) It is used in switch statement 3) It is not used in switch statement 4) Example: for(i=0;i<n;i++) { if(i==3) break; } 4) Example: for(i=0;i<n;i++) { if(i==3) continue; }
  • Input and Output Functions Input and Output Functions Unformatted Functions Formatted Functions scanf() printf() getch() getche() getchar() gets() putch() putchar() puts()
  • Formatted Functions Formatted Input: • Input data is arranged in a particular format • I/P values are taken by using scanf function • Syntax: • scanf(“control string”,arg1,arg2…argn) ; control string - includes format specifications and optional number specifying field width and the conversion character % arg1,arg2,… - address of locations where the data are stored  Example: scanf(“%3d%2d”,&a,&b);
  • An Example Program # include<stdio.h> #include<conio.h> void main() { int num1, num2; clrscr(); printf (“Enter two values:”) ; scanf(“%3d%4d”, &num1, &num2); printf (“nThe Entered Values are:%d %d”, num1, num2) ; getch(); } Output 1: Enter two values: 1342 2422 The Entered Values are: 134 2 Output 2: Enter two values: 134 2422 The Entered Values are: 134 2422
  • An Example Program # include<stdio.h> #include<conio.h> void main ( ) { float n1, n2, n3; clrscr(); printf (“Enter three values:”) ; scanf(“%f%f%f”, &n1,&n2,&n3); printf (“nThe Entered Values are:%ft%ft%f”, n1, n2, n3) ; getch(); } Output: Enter three values: 123.44 4.7 678 The Entered Values are:123.440000 4.700000 678.000000
  • An Example Program #include <stdio.h> #include <conio.h> void main() { float c, f; clrscr(); printf("Enter temp in Centigrade: "); scanf("%f",&c); f = ( 1.8 * c ) + 32; printf("Temp in Fahrenheit: %0.2f",f); getch(); } Output: Enter temp in Centigrade: 95.6 Temp in Fahrenheit: 204.08
  • An Example Program # include<stdio.h> #include<conio.h> void main ( ) { char s1[10],s2[10]; clrscr(); printf (“Enter two strings:”) ; scanf(“%3s%2s”,s1,s2); printf (“nThe Entered Values are:%st%s”,s1,s2) ; getch(); } Output: Enter two strings : hello world The Entered Values are:hel lo
  • Formatted Functions Formatted Output: • printf statement displays the information required to user with specified format • Syntax: printf(“control string”,arg1,arg2…argn) ; control string - field format which includes format specifications and optional number specifying field width and the conversion character %, blanks, tabs and newline. arg1,arg2,… - name of the variables Example: printf(“%dt%fn”,sum1,sum2);
  • Format for various output Flag output justification + (right justification) - (left justification) Width Specifier minimum field width for an output value TYPE FORMAT EXPLANATION Integer %wd w-width Float %w.cf w-width c-no. of digits after decimal point String %w.cs w-width of total characters c-no. of characters to display
  • Example • INTEGER printf(“%d”,12345); 12345 printf(“%3d”,12345); 12345 printf(“%7d”,12345); 12345 printf(“%-7d”,12345); 12345 • FLOAT printf(“%f”,123.45); 123.450000 printf(“%4.2f”,123.45); 123.45 printf(“%9.3d”,12345); 123.450 • STRING printf(“%s”,”Hello World”); Hello World printf(“%6.2s”,”Hello World”); He printf(“%1.2s”,”Hello World”); He
  • Input / Output functions #include<stdio.h> void main() { int i; float f; char c; double d; printf("Enter value for i,f,c,d:"); scanf("%d %f %c %lf",&i,&f,&c,&d); printf(“i=%dnf=%fnc=%cnd=%lf",i,f,c,d); } Output Enter value for i,f,c,d: 10 2.3 A 5.6 i=10 f=2.300000 c=A D=5.600000
  • Formatted & unformatted I/O Fundamental Data Type Data Type Conversion Symbol+Format Specifier Integer short integer %d or %i short unsigned %u long signed %ld long unsigned %lu unsigned hexadecimal %X or %x unsigned octal %o Real float %f or %g double %lf Character character %c string %s
  • Unformatted Functions Unformatted Input getch() & getche()  read a alphanumeric characters from the standard input device such as the keyboard  The character entered is not displayed by getch() function
  • Example : getch() & getche() # include<stdio.h> #include<conio.h> void main ( ) { clrscr(); printf (“Enter two alphabets:”) ; getche(); getch(); } Output:Enter two alphabets:A
  • Unformatted Functions getchar() • read a character type data from the standard input device such as the keyboard • Reads one character at a time till user press the enter key
  • Example : getchar() # include<stdio.h> #include<conio.h> void main ( ) { char c; clrscr(); printf (“Enter a character:”) ; c=getchar(); printf(“c=%c”,c); getch(); } Output: Enter a character :A c=A
  • Unformatted Functions gets() • read a string from the standard input device such as the keyboard until user press the enter key
  • Example : gets() # include<stdio.h> #include<conio.h> void main ( ) { char str[10]; clrscr(); printf (“Enter a string:”) ; gets(str); printf(“String=%s”,str); getch(); } Output: Enter a string :Hello String=Hello
  • Unformatted Functions putch() & putchar() • Prints any alphanumeric character taken by the standard input device such as the keyboard Example: char ch=„X‟; putch(ch); or putchar(ch); Output: X
  • Unformatted Functions puts() • prints the string or character array
  • Example : puts() # include<stdio.h> #include<conio.h> void main ( ) { char str[10]; clrscr(); printf (“Enter a string:”) ; gets(str); printf (“Entered string:”) ; puts(str); getch(); } Output: Enter a string :Hello Entered string:Hello