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IPC144

Introduction to Programming Using C Week 4 – Lesson 1 (Pages 38 to 46 in IPC144 Textbook). IPC144. Agenda. Additional C programming Elements TRUE / FALSE values( 1 / non-1) for loop Examples Modularity: Concept / Purpose of functions Creating a Simple Function Examples.

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IPC144

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  1. Introduction to Programming Using C Week 4 – Lesson 1 (Pages 38 to 46 in IPC144 Textbook) IPC144

  2. Agenda Additional C programming Elements • TRUE / FALSE values( 1 / non-1) • for loop • Examples • Modularity: • Concept / Purpose of functions • Creating a Simple Function • Examples

  3. TRUE / FALSE Values • So far, we have learned how to test conditions with logic such as an if / else if statement, or test conditions with an indeterminate loops such as a while or do-while statement. • In the C programming language, the TRUE result from testing a condition returns the value 1, and any value other than 1 indicates a FALSE result. Since computers work with numbers very quickly, it makes sense that the 1 or non 1 values are used to indicate TRUE or FALSE respectively.

  4. TRUE / FALSE Values • Below is an example of a program that uses values in a while loop: int x = 1, count = 0;while(x){ printf (“This is a line\n”); if ( count > 3 ) x = 0; count = count + 1;} Since the value of x is 1 (TRUE)then while statement will loop. When count become “3” thennext time condition is checked, resultbecomes 0 (FALSE) thus exits loop. Each time loop occurs, value ofcount is increased by a unit.

  5. Practice • REALITY CHECK (Week 4 – Lesson 1) • Questions #1 (Walk-thru)

  6. Loops • There are 2 category of loops: • Determinant Loops (for() statement)‏ • The number of repetitions are known. For example, repeating display of "Hello" 4 times.... • Indeterminant Loops ( while() do-while() statements)‏ • The number of repetitions is unknown. • Repetitions depend on user input. For example, repeating display of "Hello" until user (when prompted) enters number 0 to exit...

  7. Loops Inside brackets are 3 items:- x is initially given a value.- x is compared to a condition- value of x is increased by 1 for loop syntax: int x; for ( x = 1; x < 5; x++ ){ statement(s);} If condition tests TRUE,then execute statement(s)in code block. If FALSE,exit for statement…

  8. Practice REALITY CHECK (Week 4 – Lesson 1) Questions #2 (Word Problem)

  9. Modularity / Functions • As you are starting to work on your assignment #1, you may notice how quickly the coding of even a simple program can get complex. • The major technique for dealing with this complexity is to subdivide a program into a series of smaller program, sometimes called modules or functions.

  10. Modularity / Functions • Perhaps without you knowing it, you have already been using these smaller programs (i.e. functions). • When you put at the top of your program, you are instructing #include<stdio.h> the compiler to link to the “Standard Input/Ouput library” containing such functions (statements to you) as printf() or scanf().

  11. Modularity / Functions • Just like printf() and scanf() functions, you can create your own function to help complete a task. • Some functions ( like printf() and scanf() ) can contain data within the bracket to be used by the function. • Other functions, can simply run without containing data within the bracket…

  12. Modularity / Functions Here is an example: #include<stdio.h>void title(){ printf (“****************************\n”); printf (“* Report Title *\n”); printf (“****************************\n”); } main(){title();} Just like variablesmust indicate thetype of data returnedfrom a function. If nodata returned, usevoid data-type… The function title() has alreadybeen defined, and when the main()program runs, the function is runby calling it by name…

  13. Modularity / Functions • Notice in the previous example, the function appears BEFORE the main() program. • The reason for this is that the function must be “defined” prior to it being executed in the main() program. • It is like the idea of forgetting to place #include<stdio.h> at the top of your program when using printf() or scanf() functions

  14. Modularity / Functions • Most programmers prefer functions to appear after the main() program. • This can be done by using function headers that give instructions to the compiler that functions are contained in the program • See the next slide how by using a function header can allow us to re-arrange the order of the main() program and title() function.

  15. Modularity / Functions Here is an example: A function header is used to indicatethat there is a function below the main()program. Notice the function headerends with a semi-colon… #include<stdio.h> void title(); main() { title(); } void title() { printf ("****************************\n"); printf ("* Report Title *\n"); printf ("****************************\n"); }

  16. Practice REALITY CHECK (Week 4 – Lesson 1) Questions #3 (Word Problem)

  17. Homework • TASK #1 • Complete lab #3 since it is due at the beginning of this week’s lab! • TASK #2 • Study for a quiz to be held in this week’s lab based on material taught last week • TASK #3 • Complete and code the solutions for today’s REALITY CHECK QUESTIONS, as well as “hide” and repeat the walk-thru questions • TASK #4 *** Highly Recommended *** • Read ahead in IPC144 Programming Notes (Modularity / Functions).

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