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2.History of programming language, an introduction
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- 3. Language Translator Translatorsare system programms, which translate programs written in any high, or assembly language into 1’s and 0’s or machine language. There are three types of language processors or translators Assembler Compiler Interpreter Program code Language translator Machine code
- 4. Assembler Thesoftware that translates assembly code into the computer’s machine code is called assembler A program written by a programmer in assembly language is called source program After this source code has been converted into object code Language Translator
- 5. Complier Acompiler is a computer software that translates a whole program, called the source code at once into machine code (object code) Interpreter An interpreter in another type of translator used for translating a language program into machine code It takes one statement of program and translates it into a machine instruction which is immediately executed by computer Language Translator
- 6. TRANSLATION PROCESS Source Program/ code Target Program / code
- 7. Programs • Source Program: •The program we write in English langue using the editor is called Source program. • This program is given to the compiler for translation. • Target Program: • The program i.e. produced by the compiler after translating the source program is called target program. • This program is in binary form.
- 8. Variable ,keyword, constant,data type Variable: an entity that may change its value during program execution is called variable. Keyword: are words that meaning is already defined to the language. Constant: an entity that cant be changed during program execution. Data type: are used to show the type of data .
- 9. Data Type datatype is used to • Identify the type of a variable when the variable is declared • Identify the type of the return value of a function • Identify the type of a parameter passed to function
- 10. Data Type (continued) When the compiler encounters a declaration for a variable, it sets up a memory location for it An operator used on a variable or variables is legal only if The operator is defined in that programming language for a variable of that type The variable or variables involved with the operator are of the same or compatible types
- 11. Classifications of DataTypes Built-in data types Fundamental data types (int, char, double, float, void,bool) Programmer-defined data types Structure Union Enumeration
- 12. Fundamental Data Types void – used to denote the type with no values int – used to denote an integer type char – used to denote a character type float, double – used to denote a floating point type int *, float *, char * – used to denote a pointer type, which is a memory address type bool- boolean values (true,false)
- 13. Constant & Variable A constant is an entity or value that does not change during the execution of a program. an entity that may vary during program execution is called a variable. Variable names are names given to locations in memory. These locations can contain integer, real or character constants.
- 14. Rules for ConstructingIdentifiers in C The first character in the variable name must be an alphabet(A-Z,a-z) or underscore. Capital letters A-Z, lowercase letters a-z, digits 0-9, and the underscore character First character must be a letter or underscore There can be no embedded blanks Keywords cannot be used as identifiers Identifiers are case sensitive No commas or blanks are allowed within a variable name. No special symbol other than an underscore (as in gross_sal) can be used in a variable name. Identifiers refer to the names of data types, constants, variables, and functions Example: si_int m_hra pop_e_89
- 15. C constants canbe divided into two major categories Primary Constant Secondary Constant These constants are further categorized as shown in below figure
- 16. Rules for constructingInteger Constants An integer constant must have at least one digit It must not have a decimal point It can be either positive or negative If no sign precedes an integer constant, it is assumed to be positive No commas or blanks are allowed within an integer constant The allowable range for integer constant is -32768 to 32767 Example: 25, +134, 0, -600
- 17. Rules for constructingCharacter Constants A character constant is a single alphabet, a single digit or a single special symbol enclosed within single quotes The maximum length of a character constant can be 1 character Example: ‘A’,‘l’,‘5’,‘=’,‘ ’,‘.’
- 18. Definitions Initialization Declaration Variable Constant Terminator Data type Assignment operator Int a =4;
- 19. Simple C Program /*A first C Program*/ #include <stdio.h> void main() { printf("HelloWorld n"); }
- 20. Preprocessor Directives Thefirst thing to be checked by the compiler. Starts with‘#’. Tell the compiler about specific options that it needs to be aware of during compilation. There are a few compiler directives. #include <stdio.h> Tell the compiler to include the file stdio.h during compilation Anything in the header file is considered a part of the program
- 21. 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 printf function is in this file.
- 22. Simple C Program Line 2: void main() This statement declares the main function. A 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. The "void" specifies the return type of main. In this case, nothing is returned to the operating system.
- 23. Simple C Program Line3: { This opening bracket denotes the start of the program.
- 24. Simple C Program Line 4: printf("HelloWorld From Aboutn"); Printf is a function from a standard C library that is used to print strings to the standard output, normally your screen. The compiler links code from these standard libraries to the code you have written to produce the final executable. 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.
- 25. Simple C Program Line5: } This closing bracket denotes the end of the program.
- 26. Structure of aC program #include <stdio.h> void main (void) { printf(“nHello Worldn”); } Preprocessor directive (header file) Program statement #include <stdio.h> #define VALUE 10 int global_var; void main (void) { /* This is the beginning of the program */ int local_var; local_var = 5; global_var = local_var + VALUE; printf (“Total sum is: %dn”, global_var); // Print out the result } } Preprocessor directive Global variable declaration Comments Local variable declaration Variable definition
- 27. Comments Explanations orannotations that are included in a program for documentation and clarification purpose. Completely ignored by the compiler during compilation and have no effect on program execution. Starts with‘/*’ and ends with‘*/’ Some compiler support comments starting with‘//’
- 28. Statements A specificationof an action to be taken by the computer as the program executes. In the previous example, there are 2 lines following variable declaration and variable definition that terminate with semicolon‘;’. global_var = local_var +VALUE; printf (“Total sum is: %dn”, global_var); Each line is a statement.
- 29. Basic Functions AC program consists of one or more functions that contain a group of statements which perform a specific task. A C program must at least have one function: the function main. We can create our own function or use the functions that has been created in the library, in which case we have to include the appropriate header file (example: stdio.h).
- 30. In thissection, we will learn a few functions that are pre- defined in the header file stdio.h These functions are: printf() scanf() In addition to those functions, we will also learn about Format Specifier and Escape Sequence which are used with printf() and scanf().
- 31. printf() Used tosend data to the standard output (usually the monitor) to be printed according to specific format. The general form of printf( ) function is, printf ( “format string", <list of variables> ) ; <format string> can contain, %f for printing real values %d for printing integer values %c for printing character values Control string is a combination of text, format specifier and escape sequence. Example: printf(“Thank you”); printf (“Total sum is: %dn”, global_var); %d is a format specifier n is an escape sequence
- 32. scanf() Read datafrom the standard input device (usually keyboard) and store it in a variable. General format: scanf(“Control string”, &variable); The general format is pretty much the same as printf() except that it passes the address of the variable (notice the & sign) instead of the variable itself to the second function argument. Example: int age; printf(“Enter your age:“); scanf(“%d”, &age);
- 33. Summary The threeprimary constants and variable types in C are integer, float and character. A variable name can be of maximum 31 characters. Do not use a keyword as a variable name. An expression may contain any sequence of constants, variables and operators. Input/output in C can be achieved using scanf( ) and printf( ) functions.