Principles of Programming CSEB134 : BS/ CHAPTER Fundamentals of the C Programming Language

Principles of Programming CSEB134 : BS/20082 Objectives C Program development environment Elements of the C language Program comments Preprocessor directives Functions Executable Statements General form of a C program Common Programming Errors: logic/design error, syntax error, run-time error

Principles of Programming CSEB134 : BS/20083 The system software necessary to develop C application program are bundled into an integrated development environment (IDE) A typical IDE contains text editor, C compiler, preprocessor, libraries, other tools The C programming environment has 2 components: Language – features to carry out basic operations (e.g.: store data in variables, compare 2 data values, perform arithmetic operation, etc.) Libraries – routines to carry out operations not part of the language (Standard libraries – e.g.: #include & programmer-defined libraries) C Program Development Environment

Principles of Programming CSEB134 : BS/20084 IDE – Microsoft Visual C++

Principles of Programming CSEB134 : BS/20085 Prepare Compile Link Execute Steps: These steps depend on the computer, the OS, and the C IDE that you will use.

Principles of Programming CSEB134 : BS/ Prepare program (and data files) Use a text editor to type your source program statements. Assign a name to your source program file (.C) and save the file into disk storage. (optional) Use the text editor to create a data files. Assign names to the data files (.txt or.dat) and save the files 2. Compile Perform by a compiler. C compiler has 2 separate programs: the preprocessor and the translator. Preprocessor reads the source code and prepares the code for the translator. Translator translates the code into machine language.

Principles of Programming CSEB134 : BS/ Link (“Build”) As we will see later, a C program is made up of many functions. The linker assembles all the functions into final executable program (creates exe file). 4. Execute If successful, it is ready for execution and get the output otherwise debug the program

Principles of Programming CSEB134 : BS/20088 Output: A Simple C Program Example

Principles of Programming CSEB134 : BS/20089 Elements of the C language /* Example Case: Apples Author: Mdm Badariah Solemon */ #include int main() { int Qty; double Cost=0.0, Total=0.0; printf ("Enter quantity of apples purchased (in Kg):"); scanf("%d", &Qty); printf ("Enter the cost per Kg of apples (in RM per Kg):"); scanf("%lf",&Cost); Total = Cost * Qty; printf("\nTotal cost of apples = %.2f\n",Total); return 0; } preprocessor directive variable comment special symbol reserved word punctuation standard header file statement

Principles of Programming CSEB134 : BS/ Program Comments Statement in a program intended for documentation and clarification purposes Have no effect on program execution. Comments are inserted into the code using /* and */ to surround comment or // to begin comment lines. /* This is a comment */ // This is known as comment line /* The comments can span into more than one lines */

Principles of Programming CSEB134 : BS/ Preprocessor directives The C program line that begins with # provides an instruction to the C preprocessor It is executed before the actual compilation is done. Two most common directives : #include #define In our example (#include ) identifies the header file for standard input and output needed by the printf().

Principles of Programming CSEB134 : BS/ Functions Every C program has a function main The function main usually calls input/output functions – printf(), scanf(), etc. These input/output functions are discussed in Chapter 4. The word main is a C reserved word. We must not use it for declaring any other variable or constant. 4 common ways of main declaration: int main(void) { return 0; } void main(void) { } main(void) { } main( ) { }

Principles of Programming CSEB134 : BS/ The curly braces { } identify a segment / body of a program The start and end of a function The start and end of the selection or repetition block. Since the opening brace { indicates the start of a segment with the closing brace indicating the end of a segment, there must be just as many opening braces as closing braces } (this is a common mistake of beginners)

Principles of Programming CSEB134 : BS/ Statements A specification of an action to be taken by the computer as the program executes. Each statement in C needs to be terminated with semicolon (;) Example: #include void main(void) { printf(“I love programming\n”); printf(“You will love it too once ”); printf(“you know the trick\n”); }

Principles of Programming CSEB134 : BS/ Statement has two parts : Declaration The part of the program that tells the compiler the names of memory cells in a program Executable statements Program lines (excluding comments) that are converted to machine language instructions and executed by the computer. A list of statements may be enclosed in braces { } (known as compound statement) int age, total=0.0;

Principles of Programming CSEB134 : BS/ General form of a C program preprocessor directives main function heading { declarations executable statements } #include void main(void) { // statement(s); }

Principles of Programming CSEB134 : BS/ C statements can extend over more than one line. Example: printf (“\n Your coins are worth %d dollars and %d cents.\n”, dollar, change); You can write more than one statement on a line (but not recommended). Example: printf(“Enter your name:”); scanf(“%”,&Name);

Principles of Programming CSEB134 : BS/ Common Programming Errors Debugging - Process removing errors from a program Three (3) kinds of errors : 1. Syntax Error a violation of the C grammar rules, detected during program translation (compilation). statement cannot be translated and program cannot be executed

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Principles of Programming CSEB134 : BS/ Run-time errors An attempt to perform an invalid operation, detected during program execution. Occurs when the program directs the computer to perform an illegal operation, such as dividing a number by zero. The computer will stop executing the program, and displays a diagnostic message indicates the line where the error was detected ** ** depends on IDE – Ms Visual Studio: warning

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Principles of Programming CSEB134 : BS/ Logic Error/Design Error An error caused by following an incorrect algorithm Very difficult to detect - it does not cause run-time error and does not display message errors. The only sign of logic error – incorrect program output Can be detected by testing the program thoroughly, comparing its output to calculated results To prevent – carefully desk checking the algorithm and written program before you actually type it

Principles of Programming CSEB134 : BS/ Summary You learned about: C Program development environment Elements of the C language Program comments Preprocessor directives Functions Executable Statements General form of a C program Common Programming Errors: syntax error, run-time error, logic/design error.