Programming in C _unit1.docx

**[Programming in C]** 'C' is high level language and is the upgraded version of another language (Basic Combined Program Language). C language was designed at Bell laboratories in the early 1970's by Dennis Ritchie. C being popular in the modern computer world can be used in Mathematical Scientifi...

**[Programming in C]** 'C' is high level language and is the upgraded version of another language (Basic Combined Program Language). C language was designed at Bell laboratories in the early 1970's by Dennis Ritchie. C being popular in the modern computer world can be used in Mathematical Scientific, Engineering and Commercial applications. The most popular Operating system UNIX is written in C language. This language also has the features of low level languages and hence called as "System Programming Language" **[Structure of C Program:]** The sections of a C program are listed below: +-----------------------------------------------------------------------+ | Documentation section | +=======================================================================+ | Preprocessor section (link section) | +-----------------------------------------------------------------------+ | Definition section | +-----------------------------------------------------------------------+ | Global declaration | +-----------------------------------------------------------------------+ | Main() function section | | | | { | | | | Declaration part | | | | Executable part | | | | } | +-----------------------------------------------------------------------+ | Sub program section Use defined functions | | | | Function1() | | | | { | | | | } | | | | Function2() | | | | { | | | | } | +-----------------------------------------------------------------------+ 1. Documentation section 2. Preprocessor section 3. Definition section 4. Global declaration 5. Main function 6. User defined functions **1.Document section**:It includes the statement specified at the beginning of a program, such as a program\'s **name, date, description,** and **title**. It is represented as: //name of a program   Or /\*  Overview of the code  . \*/   **2.The preprocessor section** contains all the header files used in a program. It informs the system to link the header files to the system libraries. It includes **\#include\  ** **\#include\  ** The **\#include** statement includes the specific file as a part of a function at the time of the compilation. Thus, the contents of the included file are compiled along with the function being compiled. The **\#include\** consists of the contents of the standard input output files, which contains the definition of stdin, stdout, and stderr. **3.The definition section** comprises of different constants declared using the define keyword. It is given by: ### 4. Global declaration The global section comprises of all the global declarations in the program. ### 5.Main function main() is the first function to be executed by the computer. It is necessary for a code to include the main(). It is like any other function available in the C library. Parenthesis () are used for passing parameters (if any) to a function. The main function is declared as: int main() or void main() Main function is further categorized into **local declarations, statements,** and **expressions.** The variable that is declared inside a given function or block refers to as **local declarations**. main()   {   **int** i = 2;   i++;   }   // here i is the local variable **Statements** The statements refers to **if, else, while, do, for**, etc. used in a program within the main function. **Expressions** An expression is a type of formula where operands are linked with each other by the use of operators. It is given by: a - b;   a +b;   **Return function** is generally the last section of a code. But, it is not necessary to include. It is used when we want to return a value. The return function returns a value when the return type other than the void is specified with the function. For example, return 0; **[Features of C language:]** Simple, versatile, general purpose language It has rich set of Operators Program execution are fast and efficient Can easily manipulates with bits, bytes and addresses Varieties of data types are available Separate compilation of functions is possible and such functions can be called by any C program Block- structured language Can be applied in System programming areas like operating systems, compilers & Interpreters, Assembles, Text Editors, Print Spoolers, Network Drivers, Modern Programs, Data Bases, Language Interpreters, Utilities etc. **[The character set]** The character set is the fundamental raw-material for any language. Like natural languages, computer languages will also have well defined character-set, which is useful to build the programs. The C language consists of i\. Alphabets : A to Z, a to z ii\. Decimal digits : 0 to 9 iii\. Special symbols: + - \* / \^ % = & ! ( ) { } \[ \] " etc iv\) White spaces **:** This set of characters are also called as non-graphic characters because these are invisible and cannot be printed or displayed directly. These characters will have effect only when the program being executed. These characters are represented by a back slash (\\) followed by a character. +-----------------------+-----------------------+-----------------------+ | \\ n | End of a line | Transfers the active | | | | position of cursor | | \\ 0 (zero) | End of string | | | | | to the initial | | \\ t | Horizontal Tab | position of next line | | | | | | \\ v | Vertical Tab | Null | | | | | | \\ f | Form feed | Transfers the active | | | | position of cursor | | \\ r | Carriage return | | | | | to the next | | | | Horizontal Tab. | | | | | | | | Transfers the active | | | | position of cursor | | | | | | | | to the next Vertical | | | | Tab | | | | | | | | Transfers the active | | | | position of cursor | | | | | | | | to the next logical | | | | page | | | | | | | | Transfers the active | | | | position of cursor | | | | | | | | to the initial | | | | position of current | | | | line | +-----------------------+-----------------------+-----------------------+ **[Tokens in C]** Tokens in C is the most important element to be used in creating a program in C. **We can define the token as the smallest individual element in C**. For \`example, we cannot create a sentence without using words; similarly, we cannot create a program in C without using tokens in C. **Classification of tokens in C** Tokens in [C language](https://www.javatpoint.com/c-programming-language-tutorial) can be divided into the following categories: 1. Keywords 2. Identifiers 3. Strings 4. Operators 5. Constant 6. Special Characters **1.Keywords** [**Keywords in C**](https://www.javatpoint.com/keywords-in-c) can be defined as the **pre-defined** or the **reserved words** having its own importance, and each keyword has its own functionality. Since keywords are the pre-defined words used by the compiler, so they cannot be used as the variable names. If the keywords are used as the variable names, it means that we are assigning a different meaning to the keyword, which is not allowed. C language supports 32 keywords given below: **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** **2. Identifiers** [**Identifiers in C**](https://www.javatpoint.com/c-identifiers) are used for naming variables, functions, arrays, structures, etc. Identifiers in C are the user-defined words. It can be composed of uppercase letters, lowercase letters, underscore, or digits, but the starting letter should be either an underscore or an alphabet. Identifiers cannot be used as keywords. Rules for constructing identifiers in C are given below: - The first character of an identifier should be either an alphabet or an underscore, and then it can be followed by any of the character, digit, or underscore. - It should not begin with any numerical digit. - In identifiers, both uppercase and lowercase letters are distinct. Therefore, we can say that identifiers are case sensitive. - Commas or blank spaces cannot be specified within an identifier. - Keywords cannot be represented as an identifier. - The length of the identifiers should not be more than 31 characters. - Identifiers should be written in such a way that it is meaningful, short. **4. Operators** [Operators in C](https://www.javatpoint.com/c-operators) is a special symbol used to perform the functions. The data items on which the operators are applied are known as operands. Operators are applied between the operands. + , -, \*, / are the examples. 5\. **Constants** A constant is a value assigned to the variable which will remain the same throughout the program, i.e., the constant value cannot be changed. Constants are classified into 1\. **Numeric constants are** -- Integer constants and Real constants +-----------------------------------+-----------------------------------+ | **Constant** | **Example** | +===================================+===================================+ | **Integer constant** | **10, 11, 34, etc.** | +-----------------------------------+-----------------------------------+ | **Floating-point constant** | **45.6, 67.8, 11.2, etc.** | | | | | **(Real)** | | +-----------------------------------+-----------------------------------+ | **Octal constant** | **011, 088, 022, etc.** | +-----------------------------------+-----------------------------------+ | **Hexadecimal constant** | **0x1a, 0x4b, 0x6b, etc.** | +-----------------------------------+-----------------------------------+ | **Character constant** | **\'a\', \'b\', \'c\', etc.** | +-----------------------------------+-----------------------------------+ | **String constant** | **\"java\", \"c++\", \".net\", | | | etc** | +-----------------------------------+-----------------------------------+ **6.Special symbols:** Some special characters are used in C, and they have a special meaning which cannot be used for another purpose. Square brackets \[ \] Simple brackets ( ) Curly braces { } Comma (,) Asterisk (\*) Period (.) **\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*\*** **[Variables:]** Variables are containers for storing data values, like numbers and characters. A variable is a data name that may be used to store a data value. A variable may take different values at different times during execution. A variable name may consist of letters, digits anthe underscore(\_) character. - The first character of a variable should be either an alphabet or an underscore, and then it can be followed by any of the character, digit, or underscore. - It should not begin with any numerical digit. - both uppercase and lowercase letters are distinct. Therefore, we can say that variable names are case sensitive. - Commas or blank spaces cannot be specified - Keywords cannot be used - The length of the variable name should not be more than 31 characters. - should be written in such a way that it is meaningful, short. **[Data Types:]** Each variable in C has an associated data type. It specifies the type of data that the variable can store like integer, character, floating, double, etc. Each data type requires different amounts of memory and has some specific operations which can be performed over it. **The data types in C can be classified as follows:** +-----------------------------------+-----------------------------------+ | **Types** | **Description** | +===================================+===================================+ | 1. **Primitive Data Types** | Primitive data types are the most | | | basic data types that are used | | | for representing simple values | | | such as integers, float, | | | characters, etc. | +-----------------------------------+-----------------------------------+ | 2. **User Defined Data Types** | The user-defined data types are | | | defined by the user himself. | +-----------------------------------+-----------------------------------+ | 3. **Derived Types** | The data types that are derived | | | from the primitive or built-in | | | data types are referred to as | | | Derived Data Types. | +-----------------------------------+-----------------------------------+ +-----------------+-----------------+-----------------+-----------------+ | **Data Type** | **Size** | **Description** | **Example** | +=================+=================+=================+=================+ | int | 2 or 4 bytes | Stores whole | 1 | | | | numbers, | | | | | without | | | | | decimals | | +-----------------+-----------------+-----------------+-----------------+ | float | 4 bytes | Stores | 1.99 | | | | fractional | | | | | numbers, | | | | | containing one | | | | | or more | | | | | decimals. | | | | | Sufficient for | | | | | storing 6-7 | | | | | decimal digits | | +-----------------+-----------------+-----------------+-----------------+ | double | 8 bytes | Stores | 1.99 | | | | fractional | | | | | numbers, | | | | | containing one | | | | | or more | | | | | decimals. | | | | | Sufficient for | | | | | storing | | | | | | | | | | 15 decimal | | | | | digits | | +-----------------+-----------------+-----------------+-----------------+ | char | 1 byte | Stores a single | \'A\' | | | | character/lette | | | | | r/number, | | | | | or ASCII values | | +-----------------+-----------------+-----------------+-----------------+ **Void - void** type has no value. It is used to specify the type of functions. When a function does not return a value to calling function, the type of function is said to be void. **[Declaration of variables:]** A variable declaration (definition) tells the compiler where and how much storage to create for the variable. A variable declaration provides assurance to the compiler that there exists a variable with the given type and name so that the compiler can proceed with further compilation without requiring complete detail about the variable. A variable definition has its meaning at the time of compilation only, the compiler needs actual variable definition at the time of linking the program. A variable declaration specifies a data type and contains a list of one or more variables of that type as follows. int a; int a,b; char c; float avg; **The general form or syntax to declare a variable** is -- data type variablename1, variablename 2,......variablename n; example: int a; int m1,m2,m3; Variables can be initialized (assigned an initial value) in their declaration. The initializer consists of an equal sign followed by a constant expression as follows -- datatype variable name = value; **example:** // declaration with initialization int x = 10; // the variable x has the value \'x\' char x = \'x\'; // define and initialize two variables int d = 3, f = 5; **[User Defined type declaration]** C supports **"type definition**" that allows users to define an identifier that would represent an existing data type. The user defined data type identifier can later be used to declare variables. The general form is - typedef *type* identifier; example : typedef int units; here units symbolizes int and this can be used to declare variables as follows- units batch1, batch2; // batch1,batch2 are declared as int **Another user defined data type is** **enumerated data type** which can be used to declare variables that can have one of the values enclosed within the braces. The general form is enum identifier (value1, value2,....vn); enum identifier v1,v2...vn; enumerated variables v1, v2... can have one of the values value1, value2... **[Defining symbolic constants]** ***Identifiers* ** used to represent fixed values in programs using *symbolic constants* in the C programming language. These parameters are frequently used to increase the ***readability*, *maintainability*, and *modifiability* of code**, which may be numerical or not. The C language\'s ***\"\#define\"*** command is used to declare *symbolic constants*. Symbolic constants are nothing more than a label or name that is used to represent some fixed value that never changes throughout the course of a program. For example, one might define PI as a constant to represent the value 3.14159. **Syntax:** Syntax for defining a symbolic constant in C: \#define  MAX 100   -- --