C Programming Notes PDF

UNIT I CHAPTER I  1.1 OVERVIEW OF C C Language is a Structured High-level Machine independent language History of C The root of all modern languages is ALGOL (introduce in 1960s).  ALGOL uses a structure programming. ALGOL is popular in Europe Computer scientists lik...

UNIT I CHAPTER I  1.1 OVERVIEW OF C C Language is a Structured High-level Machine independent language History of C The root of all modern languages is ALGOL (introduce in 1960s).  ALGOL uses a structure programming. ALGOL is popular in Europe Computer scientists like Corrado Bohm, Guiseppe Jacopini and Edsger Dijkstra popularised the structured programming concepts. In 1967, Martin Richards developed a language called BCPL (Basic Combined Programming Language) Contn… Primarily BCPL is developed for system software.  In 1970, Ken Thompson created a new language called B.  B is created for UNIX os at Bell Laboratories.  Both BCPL and B were “typeless” languages  C was developed by Dennis Ritchie at the Bell Laboratories in 1972.  Added new features and concepts like “data types”. C was evolved from ALGOL, BCPL and B.  It was developed along with the UNIX operating system.  It was strongly integrated with the UNIX operating system.  In 1983 American National Standards Institute (ANSI) appointed a technical committee to define a standard for C. The committee approved a version of C in December 1989 which is now known as ANSI C.  In 1990 International Standards Organization (ISO) has approved C and this version of C is referred to as C89.  1.2 IMPORTANCE OF C It is a robust language whose rich set of built-in functions and operators can be used to write any complex program. The C compiler combines the capabilities of an assembly language with the features of a high-level language and therefore it is well suited for writing both system software and business packages. Programs written in C are efficient and fast. C is highly portable. C language is well suited for structured programming. Ability to extend itself. A C program is basically a collection of functions that are supported by the C library.  1.3 SAMPLE PROGRAM 1 main() ---------------------------------- Function Name {------------------------------------------- Start of Program printf(“ Hello Program “); --------- Program Statements } ------------------------------------------- End of Program Output Hello Program  SAMPLE PROGRAM 2 main() { int number; float amount; number =100; amount=30.75+75.35; printf(“%d\n”,number); printf(“%5.2f”,amount); } Output 100 106.10 1.4 BASIC STRUCTURE OF C PROGRAM Documentation Section optional Link Section Definition Section optional Global Declaration Section optional main() Function Definition { Declaration part Executable part } Subprogram Section optional Function 1 Function 2 --- User-defined functions --- Function n Documentation section A set of comment lines giving the name of the program, the author and other details. Link section Provides instructions to the compiler to link functions from the system library. Definition section defines all symbolic constants. Global declaration section There are some variables that are used in more than one function. Such variables are called global variables. Global variables are declared in the global declaration section that is outside of all the functions. Also declares all the user-defined functions. Main() function Every c program must contain main() function section. This section contains two parts Declaration part Executable part These two parts must appear between the opening and closing braces ({ }). Declaration part Declares all the variables used in the executable part Executable part There is atleast one statement in the executable part. The closing brace of main function sections is the logical end of the program. All statements in the declaration and executable parts end with the semicolon(;). Subprogram section contains all user-defined functions that are called in the main function. User-defined functions are generally placed immediately after the main function , although they may appear in any order. EXECUTING A ‘C’ PROGRAM Steps 1. Creating the program. 2. Compiling the program. 3. Linking the program with functions that are needed from the C library 4. Executing the program. 1.5 Process of Compiling and Running a C program System Ready Program Code Enter Program Source Program Edit Source Program C Compiler Compile Source Program Syntax Yes Errors ? NO Object Code Link With System System Library Library Executable Object Code Input Data Execute Object Code Data Error Logic Error Logic and Data Errors? NO Errors Correct Output Stop  1.6 WRITING AND EXECUTING A C PROGRAM IN UNIX Create a c program  write the c-program using some text editors (eg. vi or ed) – ed filename – vi filename  The program must be entered into a file.  The file name can consists of letters, digits and special character, followed by dot(.) and a letter c. Example firstcpgm.c  If the file existed before, it is loaded.  Otherwise the file has to be created so that it is ready to receive the new program.  The program that is entered into the file is called source program. Compiling and linking  use an existing compiler (gcc, cc etc) to compile your program an make an executable Example  cc filename  cc filename1, filename2, filename3 ……… Common options: –lm : library math -c : Compiles without linking. binaries are saved as "filename.o" -o exename: compiled binary with specified filename. (a.out default) cc –o myprog firstprog.c Execute the program a.out  UNIT I CHAPTER II  2.1. CHARACTER SET The characters that can be used to form words, numbers and expressions. Letters Digits Upper case :A---Z, Lower case : a--z 0---9 Special Characters , (comma).(period) ;(semicolon) & (ampersand) ^ (caret) : (colon) ? (question mark) (asterisk) - (minus sign) ‘ (apostrophe) “ (quotation mark) + (plus sign) < (less than sign) ! (exclamation mark) | (vertical bar) > (greater than sign) ( (left parenthesis) / (slash) \ (back slash) ) (right parenthesis) [ (left bracket) ~ (tilde) _ (under score) ] (right bracket) # (number sign) $ (dollar sign) % (percent sign) { (left brace) } (right brace) White spaces Bank space, Horizontal tab Carriage return, New line Form feed  2.2. C TOKENS Individual words and punctuation marks are called tokens. Smallest individual units are known as C tokens. C TOKENS Keywords Constants Strings Operators Special Identifiers Symbols  2.2.1 KEYWORDS AND IDENTIFIERS  All keywords have fixed meaning and these meanings cannot be changes. Keywords serve as basic building blocks for program statements. There are certain words reserved for doing specific task, these words are known as reserved word or keywords. These words are predefined and always written in lower case or small letter. These keywords cannot be used as a variable name as it assigned with fixed meaning.  ANSI C 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 Identifiers are user defined word used to name of entities like variables, arrays, functions, structures etc. Rules for naming identifiers are: 1) Must consists of alphabets (both upper and lower case), digits and underscore (_) sign. 2) First characters must be an alphabet or underscore. 3) Only first 31 characters are significant. 4) Cannot use a keyword. 5) Must not contain whitesoace. C is a case sensitive, the upper case and lower case considered differently, for example code, Code, CODE etc. are different identifiers. identifiers are generally given in some meaningful name such as value, net_salary, age, data etc. Some invalid identifiers are 5cb, int, res#, avg no etc.  2.2.2 CONSTANTS Fixed values that do not change during the execution of a program. CONSTANTS Numeric Constants Character Constants Single Integer Real String Character Constants Constants Constants Constants Integer Constants An integer constant refers to a sequence of digits. Integer Constants Decimal Hexadecimal Octal Integers Integers Integers Consists of a Consists of any A sequence of digits set of digits, 0 combination of digits preceded by 0x or 0X. through 9, preceded from 0 to 7,while They may include by an optional – or + leading 0. Alphabet A through F. sign. Example: The letter A through F Example: 123, 037, 0, 0437 represents 0 through -123,0, +73 15. Example: 0X2,ox9F,oxABCD Real Constants These numbers are decimal notation,havinfg whole number followed by a decimal point and the fractional part. It is possible to omit digits before the decimal part, or digits after the decimal part. A real number may expressed in exponential notation. mantissa e exponent The mantissa is either a real number expressed in decimal notation or integer. The exponent is an integer number with an optional + or – sign. The letter e can be written in either uppercase or lowercase. Embedded white space is not allowed. The e notation is called floating-point form. Floating –point constants are represented as double-precision quantities. f or F --- Single-precision l or L --- Double-precision Valid real numbers: 78688L,25636l,444.643f,321.55F,2.5e+05,374e-04 Invalid real numbers: 1.5E+0.5,$25,ox7B,7.5 e -0.5,1,00,00.00 Character Constants Character Constants Single Character String Constants Constants single character enclosed A sequence of characters within a pair of single quote. Enclosed in double quotes. Example: The characters may be letters ‘5’, ‘ a’, ‘ ’ numbers, special characters and blank spaces. Example: “Hello World!”, “25”, “5”, “3+5” Note: 5 ≠ ‘5’ ≠ “ 5”  5 –Integer Constant ‘5’ – single Character Constant “5”- String Contant Backslash character constants - used in output functions - each one of them represents one character. - these characters combinations are known as escape sequences  SYMBOLIC CONSTANTS Symbolic constant is defined as follows #define symbolic_name value-of-constant Example: #define PI 3.14159 #define MAXMARKS 100 Rules 1) Symbolic names have the same form as variable names. 2) No blank space between the # sign define is permitted. 3) # must be the first character in the line. 4) A blank space is required between #define and symbolic name and between the symbolic name and constant. 5) #define statements must not end with a semicolon. 6) After definition, the symbolic name should not be assigned any other value within the program by using an assignment statement. 7) Symbolic names are not declared for data types. Its data type depends on the type of constant. 8) #define statements may appear anywhere in the program but before it is referenced in the program.  2.2 VARIABLES Variable is a data name which is used to store data value. The value of the variable can be change during the execution. The rule for naming the variables is same as the naming identifier. Rules : 1) They begin with a letter. Some systems permit underscore as the first character. 2) Upto 31 characters (ANSI) 3) Case Sensitive ie. Uppercase and lowercase are significant. A ≠ a 4) It should not be a keyword 5) White space is not allowed. Examples: Valid variable names: sum, Sum, SUM, a1,odd_sum Invalid Variable names: 1a,odd-sum,a%,1st,(area)  2.3 DATA TYPES Data types refer to an extensive system used for declaring variables or functions of different types before its use. The type of a variable determines how much space it occupies in storage and how the bit pattern stored is interpreted. C DATA TYPES Primary or Fundamental Derived Data User-defined Data Types Type Data Type  PRIMARY OR FUNDAMENTAL DATA TYPES Primary Data Types Integral Type Floating point Types void Character Long Integer float char double signed char unsigned char double unsigned signed int unsigned int short int unsigned short int long int unsigned long int  INTEGER TYPES Integer occupy one word of storage, and word sizes of machines vary (16 or 32 bits). The signed integer uses one bit for sign and 15 bits for the magnitude of the number. Smallest to largest. short int int long int FLOATING POINT TYPE Floating point numbers are stored in 32-bits, with 6 digits of precision. float double long double CHARACTER TYPE A single character can be defined as a character (char) type data. Characters are stored in 8 bits of internal storage. The qualifier signed or unsigned may be explicitly applied to char. VOID TYPE has no values. Used to specify the type of functions. The type of function is said to be void when it does not return any value to the calling function. Play the role of a generic type, ie it can represent any of the other stamdard type.  TYPE KEYWORD SIZE RANGE (BITS) char or 8 -128 to 127 Character signed char unsigned char 8 0 to 255 int or 16 -32,768 to 32767 signed int unsigned int 16 0 to 65535 short int or 8 -128 to 127 Integer signed short int unsigned short int 8 0 to 255 long int or 32 -2,147,483,648 to signed long int 2,147,483,647 unsigned long int 32 0 to 4,294,967,295 float 32 3.4E-38 to 3.4E+38 double 64 1.7E-308 to 1.7E+308 Real long double 80 3.4E-4932 to 1.1E+4932  2.4 DECLARATION OF VARIABLES Declaration does two things 1. It tells the compiler what the variable name is. 2. It specifies what type of data the variable will hold. Primary type declaration A variable can be used to store a value of any data type. data_type v1,v2,v3,….,vn; v1,v2,v3,…vn are the name of the variables. Variables are separated by commas. Declaration statement end with a semicolon. Example: int count; float total; double ratio; User-defined type declaration 1. “type definition” – allows users to define an identifier that would represent an existing data type. The user-defined data type identifier can be used to declare variables later. typedef type identifier; Where type refers to an existing data type, identifier refers to the new name given to the data type. The existing data type may belong to any class of type, including the user- defined type. Example: typedef int units; typedef float marks; Here, units symbolizes int and marks symbolizes float. units batch1,batch2; marks name; Advantage of typedef We can create meaningful data type names for increasing the readability of the program. 2. “enumerated” Enum identifier (value1,value2,…..,valuen); The ‘identifier’ is a user-defined enumerated data type which can be used to declare variables That can have one of the values enclosed within the braces – enumerated constants. enum identifier v1,v2,…..,vn; The enumerated variables v1,v2,…..,vn can have one of the values value1,value2,…..,valuen. V1=value3; V3=value5; Example: Enum day(Moday,Tuesday,…..,Sunday); Enum day week_st,week_end; Week_st=Monday; Week_end=Friday;  2.5 DECLARATION OF STORAGE CLASS Storage class provides the information about their location and visibility. The storage class decides the portion of the program within which the variables are recognized. i. Global variables: Global variables are known throughout the program. The variables hold their values throughout the programs execution. Global variables are created by declaring them outside of any function. It need not be declared in other function. A global variable is also known as external variable. Global variables are defined above main () in the following way: int n, sum; int m,l; char letter; main() { } it is also possible to pre-initialize global variables using the = operator for assignment. Example: float sum = 0.0; int n= 0; char c=`a'; main() { } This is the same as: float sum; int n; char letter; main() { sum = 0.0; n= 0; c=`a'; } is more efficient. C also allows multiple assignment statements using = Example: a = b = 1; This is same as a = 1; b = 1; Note : The assignment is valid if all the variable types are the same data type. ii. Local variables: Variable that are declared inside a function are called “local variables”. Local variables are referred to as “automatic variables”. Local variables may be referenced only by statements that are inside the block in which the variables are declared. Local variables exist only while the block of code in which they are declared is executing. Local variables are not known to other function block. Any changes are made in local variables does not affect its value in the other. Example: void func1 (void) { Int n; n = 0; } void func2 (void) { int n; n = 99; } The integer variable n is declared in func1 () & func2 (). n is only known to the code with in the same block as variable declaration. Storage class There are four types of storage class specifiers 1. auto 2. register 3. static 4. extern  Automatic Storage class meaning initialization Garbage value Local variable known to the function in auto (undefined which it is declared. Default is auto. value) register Local variable which is stored in the register -- Local variable which exists and retains its Static value even after the control is transferred to 0 the calling function. Global variable known to all function in the extern 0 file Declaring a variable as constant The value of the variable to remain constant during the program execution. The variable can be declared with the qualifier const at the time of initialization. const data_type variable_name=constant; Example const int n=50; The value of n cannot be modified.  2.6 ASSIGNING VALUE TO VARIABLES Variablename = constant; Example: n=5; count=count+1; datatype variable_name=constant; Example: int n=5; float x=5.5;  CHAPTER III OPERATORS AND EXPRESSIONS  3.1. INTRODUCTION A symbol use to perform some operation on variables, operands or with the constant is known as operator. Some operator required 2 operand or Some required single operand to perform operation. C operators can be classified into a number of categories. 1) Arithmetic operators 2) Relational operators 3) Logical operators 4) Assignment operators 5) Increment and decrement operators 6) Conditional operators 7) Bitwise operators 8) Other operators An expression is a sequence of operands and operators that reduces to a single value. The value can be any type other than void.  3.1.1. ARITHMETIC OPERATORS Operator Meaning Expression values Integer Real Addition or unary Arithmetic Arithmetic + plus a+b a=10, b=3 13 13.0 - Subtraction or a-b a=10, b=3 7 7.0 unary minus a*b a=10, b=3 30 30.0 * Multiplication a=10, b=3 3 3.3333333 a/b / Division a=15, b=3.0 5(lhs int) 5.0 Modulo division a=10, b=3 1 % Cannot be a=-14, b=3 -2 used with a%b a=-14, b=-3 -2 real operands a=14, b=-3 2  3.1.2 RELATION OPERATORS Relation operators and meaning Syntax ae-1 relational operator ae-2 Operator Meaning Examples == Equal Relational Result != Not equal expression 4.510 false 4.5>=10 false  3.1.3 LOGICAL OPERATORS Logical Operators and Meaning Syntax Op-1 logicaloperator op-2 Operators Meaning Truth Table && Logical AND Value of the Expression Op-1 Op-2 Op-1&&op-2 Op-1||op-2 || Logical OR Non- Non- 1 1 ! Logical NOT zero zero Non- zero 0 0 1 Non- 0 zero 0 1 0 0 0 0  3.1.4 ASSIGNMENT OPERATORS Assignment Operators and Meaning Operators and Examples  Assignment operators are used to assign the result of an expression to a variables. Operators Example Equivalent Syntax += a+=1 a=a+1 v op=exp; Where v is a variable, exp is an expression and -= a-=1 a=a-1 op is a binary arithmetic operator. *= a*=n+1 a=a*(n+1) The assignment statement /= a*=n+1 a=a/(n+1) v op=exp; %= a%=b a=a%b is equivalent to v=v op (exp); Advantages 1. What appears on the left-hand side need not be repeated and therefore it becomes easier to write. 2. The statement is more concise and easier to read. 3. The statement is more efficient.  3.1.5 INCREMENT & DECREMENT OPERATORS operators 1. Pre-increment & decrement-prefix ++ and -- Examples 2. Post-increment & decrement-postfix ++ and -- m=5;  Prefix operator adds 1 to the operand and then the result is assigned to the variable on left.  Postfix operator first assigns the value to the operator Expression Result M variable on left and then increments the value operator. Prefix y=++m y=6 m=6 Rules ++ 1. Increment and decrement operators are unary operators. Prefix -- y=--m y=4 m=4 2. When postfix ++ (or --) is used with a variable in an expression, the expression is evaluated Postfix y=m++ y=5 m=6 first using the original value of the variable and ++ then the variable is Increment (or decrement) by one. Postfix - y=m-- y=5 m=4 3. When prefix ++ (or decrement) is used in an - expression, the variable is incremented (or decremented) first and then the expression is evaluated using the new value of the variable. 4. The precedence and associatively of ++ and – operators are same as those of unary + and unary -.  3.1.6 CONDITIONAL OPERATOR Operator and syntax Example A ternary operator pair “?:” is called a=10; conditional operator. b=15; Syntax x=(a>b)?a:b; exp1?exp2:exp3; output Where exp1, exp2 and exp3 are x=10 expression. The above code is equivalent to  Exp1 is evaluated first. if (a>b)  If it is true(nonzero) then the x=a; expression exp2 is evaluated and else becomes the value of the expression. y=b;  Otherwise exp3 is evaluated and its value becomes the value of the expression.  3.1.7 BITWISE OPERATORS Bitwise operators  Bitwise operators are used for Operators Meaning manipulating data at bit level.  These operators are used for testing & Bitwise AND the bits, or shifting them right or left. | Bitwise OR  Bitwise operators may not be applied ^ Bitwise exclusive to float or double. OR > Shift right  3.1.8 SPECIAL OPERATORS Special operators are 1. comma operator (,) sizeof opeartor 2. sizeof operator  The sizeof is a compile time operator 3. pointer operators (& and *) and when used with an operand, it 4. member selection operators(.,->) returns the number of bytes the operand occupies. Comma operator  The operand may be a variable, a  Comma operator can be used to link the constant or a data type qualifier. related expression together. Examples:  A comma-linked list of expressions are m=sizeof(sum); evaluated left to right and the value of right-most expression is the value of the n=sizeof(long int); combined expression. k=sizeof(235l); Example:  The sizeof operator normally used to z=(x=10, y=15, x+y); determine the lengths of arrays and  First assigns the value 10 to x, then 15 structures when their sizes are not to y and finally 25 to z. known to the programmer.  Comma operator has the lowest  It is also allocate memory space precedence of all operators. dynamically to variables during program execution. Exchanging values: t=x, x=y, y=t;  3.2 ARITHMETIC EXPRESSION  An arithmetic expression is a Evaluation of expressions combination of variables, constants  Expressions are evaluated using an and operators arranged as per the assignment statement of the form syntax of the language. Variable=expression;  C does not have the operator for  Variable is any valid c variable name. exponentiation.  When the statement is encountered, Algebraic C expression the expression is evaluated first and expression the result then replaces the previous a*b /c value of the variable on the left hand side. a x b-c a*b-c  All the variables used in the (m+n)(x+y) (m+n)*(x+y) expression must be assigned values 3x2+2x+1 3*x*x+2*x+1 before evaluation is attempted. a/b+c Example: x = a * b – c;  Rules for evaluation of expressions. First, Parenthesized sub expression from left to right are evaluated. If parentheses are nested, the evaluations begins with the innermost sub expression. The precedence rule is applied in determining the order of application of operators in evaluating sub expression. The associative rule is applied when two or more operators of the same precedence level appear in a sub-expression. Arithmetic expressions are evaluated from left to right using the rules of precedence. When parentheses are used, the expressions within the parentheses assume highest priority. Priority levels High priority * / % Low priority  + -  3.3 OPERATOR PRECEDENCE AND ASSOCIATIVITY Operator Description Associativity Rank () [] function call and array element reference left to right 1 + - ++ -- ! unary plus ,unary minus, increment, right to left 2 ~*& decrement, logical negation, ones sizeof complement, pointer reference, address, (type) size of an object and type cast */% multiplication, division and modulo left to right 3 division +- addition and subtraction left to right 4 > left shift and right shift left to right 5 < >= less than, less than or equal to, greater left to right 6 than and greater than or equal to == != equal to and not equal to left to right 7 & bitwise and left to right 8 ^ bitwise xor left to right 9 | bitwise or left to right 10 Operator Description Associativity rank && Logical AND Left to right 11 || Logical OR Left to right 12 ?: Conditional expressions right to Left 13 = *= /= %= Assignment operations right to Left 14 += -= &= ^= |= = , Comma operator Left to right 15 Rules of precedence and associativity Precedence rules decides the order in which different operators are applied Associative rule decides the order in which multiple occurrences of the same level operator are applied.  3.4. TYPE CONVERSION Type conversion Implicit type Explicit Type conversion conversion 3.4.1 Implicit Type Conversion Automatic type conversion is called implicit type conversion. If the operands are of different types, the lower type is automatically converted to the higher type before the operations proceeds. The result is of the higher type. long double Conversion Hierarchy double float unsigned Conversion long int Hierarchy long int unsigned int int short char 3.4.2 Explicit Type Conversion  The process of local conversion is called explicit type conversion or casting a value. Syntax (type-name)expression  Where type-name is one of the standard c data types.  The expression may be a constant , variable or an expression. Example: x=(int) 7.5; 7.5 converted to integer by truncation a=(int)21.3/(int)4.5; evaluated as 21/4 and the result would be 5 b=(double) sum/n;  divison is done in floating point mode. y=(int)(a+b);  the result of a+b is converted to integer. z=(int)a+b; a is converted to integer and then added to b  3.5 MATHEMATICAL FUNCTION FUNCTION MEANING acos(x) Arc cosine of x asin(x) Arc sine of x atan(x) Arc tangent of x atan2(x,y) Arc tangent of x/y cos(x) Cosine of x sin(x) Sine of x tan(x) Tangent of cosh(x) Hyperbolic cosine of x sinh(x) Hyperbolic sine of x tanh(x) Hyperbolic tangent of x ceil(x) X runded up to the nearest integer floor(x) X rounded down to the nearest integer pow(x,y) X to the power of y sqrt(x) Square root of x, x>=0  REFRENCES E. Balagurusamy, ”Programming in ANSI C”, Seventh Edition, McGraw Hill Education India Private Ltd, 2017. https://image.slidesharecdn.com/1-overviewandhistoryofc