C basics 4 std11(GujBoard)

Chapter 3: Introduction to C Programming LanguageC development environmentA simple program exampleCharacters and tokensStructure of a C programcomment and preprocessor directivesbasic data typesdata declarationsstatementsBasic functions

Program iscreated in theEditor and stored on Disk. EditorPhase 1 :DiskDiskCompiler creates objectcode and stores it on Disk.CompilerPhase 3 :DiskLinker links object code with libraries, creates a.out and stores it on Disk. Linker Phase 4 :DiskC Development EnvironmentPreprocessorprogramprocesses the code. PreprocessorPhase 2 :

Primary MemoryLoader Phase 5 :Loader putsProgram inMemory:.Primary MemoryC P UPhase 6 :CPU takes eachinstruction and executes it, storingnew data values asthe program executes.:.

From code to executablesSource CodePre-processor CompilerAssembly Code AssemblerLibraries Object Code Linker Executable Code

A Simple Program Example#include <stdio.h>main(){ printf("Programming in C is easy.\n");}Sample Program OutputProgramming in C is easy.

NOTE ABOUT C PROGRAMSIn C, lowercase and uppercase characters are very important! All commands in C must be lowercase. The C programs starting point is identified by the word main() This informs the computer as to where the program actually starts. The brackets that follow the keyword main indicate that there are no arguments supplied to this program (this will be examined later on). The two braces, { and }, signify the begin and end segments of the program.

The purpose of the statement #include <stdio.h> is to allow the use of the printf statement to provide program output. Text to be displayed by printf() must be enclosed in double quotes. The program has only one statement printf("Programming in C is easy.\n"); printf() is actually a function (procedure) in C that is used for printing variables and text. Where text appears in double quotes "", it is printed without modification. There are some exceptions however.

This has to do with the \ and % characters. These characters are modifiers, and for the present the \ followed by the n character represents a newline character. Thus the program printsProgramming in C is easy.and the cursor is set to the beginning of the next line. As we shall see later on, what follows the \ character will determine what is printed, ie, a tab, clear screen, clear line etc. Another important thing to remember is that all C statements are terminated by a semi-colon ;

Summary of major points so far

program execution begins at main()

keywords are written in lower-case

statements are terminated with a semi-colon

text strings are enclosed in double quotesCharacters and tokensCharacters are the basic building blocks in C program, equivalent to ‘letters’ in English languageIncludes every printable character on the standard English language keyboard except `, $ and @Example of characters:Numeric digits: 0 - 9Lowercase/uppercase letters: a - z and A - ZSpace (blank)Special characters: , . ; ? “ / ( ) [ ] { } * & % ^ < > etc

A token is a language element that can be used in forming higher level language constructsEquivalent to a ‘word’ in English languageSeveral types of tokens can be used to build a higher level C language construct such as expressions and statementsThere are 6 kinds of tokens in C:Reserved words (keywords)IdentifiersConstantsString literalsPunctuatorsOperators

Reserved WordsKeywords that identify language entities such as statements, data types, language attributes, etc.Have special meaning to the compiler, cannot be used as identifiers in our program.Should be typed in lowercase.Example: const, double, int, main, void, while, for, else (etc..)

IdentifiersWords used to represent certain program entities (program variables, function names, etc).Example:int my_name; my_name is an identifier used as a program variablevoid CalculateTotal(int value)CalculateTotal is an identifier used as a function name

ConstantsEntities that appear in the program code as fixed values.4 types of constants:Integer constantsPositive or negative whole numbers with no fractional partExample: const int MAX_NUM = 10;const int MIN_NUM = -90;Floating-point constantsPositive or negative decimal numbers with an integer part, a decimal point and a fractional partExample:const double VAL = 0.5877e2; (stands for 0.5877 x 102)

Character constantsA character enclosed in a single quotation markExample:const char letter = ‘n’;const char number = ‘1’;printf(“%c”, ‘S’);Output would be: SEnumerationValues are given as a listExample:

String LiteralsA sequence of any number of characters surrounded by double quotation marks. Example:“REFORMASI”“My name is Salman”Example of usage in C program:printf(“My room number is BN-1-012\n”);Output: My room number is BN-1-012

Punctuators (separators)Symbols used to separate different parts of the C program.These punctuators include:[ ] ( ) { } , ; “: * #Usage example:

OperatorsTokens that result in some kind of computation or action when applied to variables or or other elements in an expression.Example of operators:* + = - /Usage example:result = total1 + total2;

Structure of a C programPreprocessor directive (header file)Program statement}Preprocessor directiveGlobal variable declarationCommentsLocal variable declarationVariable definition

CommentsExplanations or annotations 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 ‘//’

Preprocessor DirectivesThe first 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. But only 2 of them will be discussed here.#include <stdio.h>Tell the compiler to include the file stdio.h during compilationAnything in the header file is considered a part of the program#define VALUE 10Tell the compiler to substitute the word VALUE with 10 during compilation

Basic Data Types3 examples of basic data types:int (used to declare numeric program variables of integer type)char (used to declare character variable)double (used to declare floating point variable)In addition, there are float, void, short, long, etc.Declaration: specifies the type of a variable.Example: int local_var;Definition: assigning a value to the declared variable.Example: local_var = 5;

A variable can be declared globally or locally.A globally declared variable can be accessed from all parts of the program.A locally declared variable can only be accessed from inside the function in which the variable is declared.

StatementsA specification of 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: %d\n”, global_var);Each line is a statement.

Basic FunctionsA C 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).

In this section, we will learn a few functions that are pre-defined in the header file stdio.hThese functions are:printf()scanf()getchar() & putchar() In addition to those functions, we will also learn about Format Specifier and Escape Sequence which are used with printf() and scanf().

printf()Used to send data to the standard output (usually the monitor) to be printed according to specific format.General format:printf(“control string”, variables);Control string is a combination of text, format specifier and escape sequence.Example:printf(“Thank you”);printf (“Total sum is: %d\n”, global_var);%d is a format specifier\n is an escape sequence

Format SpecifierTells the printf() function the format of the output to be printed put.

C basics 4 std11(GujBoard)

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