structure of a c program - slideshare.pptx
- 1. 20CSS01 – Programming for Problem Solving • Easy to learn & Opportunity to work on open source projects. • Can be compiled on variety of computers • Structured language • Extensible by adding functions • Understand the internal architecture of a computer, how computer stores and retrieves information. • Easier to learn other programming languages like Java, Python, etc. • Some of the largest open-source projects Linux kernel, Python interpreter, SQLite database, etc. are written in C Why C Became Popular? Or Why Learn C ?
- 2. Compiler, Interpreter & Assembler • A computer understands instructions in machine code, i.e. in the form of 0s and 1s. It is a tedious task to write a computer program directly in machine code. The programs are written mostly in high-level languages are called source code. • These source code cannot be executed directly by the computer and must be converted into machine language to be executed. • Compilers & Interpreters translate programs written in high-level languages into machine code that a computer understands. • Assemblers translate programs written in low-level or assembly language into machine code and its machine-dependent
- 3. C Compiler • The source code written in source file is the human readable source for your program. It needs to be "compiled", into machine language so that your CPU can actually execute the program as per the instructions given. • The compiler compiles the source codes into final executable programs. • The most frequently used and free available compiler is the GNU C/C++ compiler, • Ctrl-F9. – Compilation ; Alt + F9 - Run
- 4. Structure of a C program
- 5. Documentation Section • We can give commands about program like author name, creation or modified date. • The information written in between /* */ or // is called as comment line. • These lines are not considered by the compiler while executing. Preprocessor Directives The C preprocessor is a macro processor that is used automatically by the C compiler to transform your program before actual compilation (Proprocessor direcives are executed before compilation.). It is called a macro processor because it allows you to define macros
- 6. Preprocessing directives are lines in your program that start with #. The # is followed by an identifier that is the directive name. For example, #define is the directive that defines a macro. Eg : • #include • #define
- 7. Header Files Inclusion or Linker section • The first and foremost component is the inclusion of the Header files in a C program. • A header file is a file with extension .h which contains C function declarations and macro definitions to be shared between several source files. Some of C Header files: – stddef.h – Defines several useful types and macros. – stdint.h – Defines exact width integer types. – stdio.h – Defines core input and output functions – stdlib.h – Defines numeric conversion functions, pseudo-random network generator, memory allocation – string.h – Defines string handling functions – math.h – Defines common mathematical functions
- 8. • Main Method Declaration: The next part of a C program is to declare the main() function • Variable Declaration: ⮚ It refers to the variables that are to be used in the function. ⮚ In the C program, no variable can be used without being declared and to be declared before any operation in the function. • Body : The body of a function in the C program, refers to the operations that are performed in the functions. It can be anything like manipulations, searching, sorting, printing, etc. int main() { int a; printf("%d“,a); }
- 9. Character Set • The character set refers to a set of all the valid characters that we can use in the source program for forming words, expressions, and numbers. • It denotes any alphabet, digit or special symbol used to represent information. • They include digits, alphabets, special symbols, etc. The C language provides support for about 256 characters. • The characters in C are grouped into the following two categories: 1. Source character set a. Alphabets b. Digits c. Special Characters d. White Spaces 2. Execution character set - Escape Sequence
- 11. Execution Character Set • Certain ASCII characters are unprintable, which means they are not displayed on the screen or printer. Those characters perform other functions aside from displaying text. Examples are backspacing, moving to a newline, or ringing a bell. • They are used in output statements. Escape sequence usually consists of a backslash and a letter or a combination of digits. • An escape sequence is considered as a single character but a valid character constant. Execution characters set are always represented by a backslash () followed by a character. • Each one of character constants represents one character, although they consist of two characters. These characters combinations are called as escape sequence.
- 12. Tokens • The token is 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. • Therefore, we can say that tokens in C is the building block or the basic component for creating a program in C language
- 13. Identifiers • Used for naming variables, functions, arrays, structures, etc. • Identifiers in C are the user-defined words. • Identifiers cannot be used as keywords. Rules while naming c identifiers • 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. • 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, and easy to read.