ATS 315: Working With Loops in C Loops in C ATS 315

ATS 315: Working With Loops in C Loops Are used to perform some action multiple times. Are crucial to most C programs that are useful.

ATS 315: Working With Loops in C Two Main Kinds of Loops Loops that run a specific number of times. –“for” loops Loops that run a flexible number of times, if at all. –“while” loops

ATS 315: Working With Loops in C “for” loops Require a “counter” that keeps track of how many times the loop has run. Typically this is an integer, but it doesn’t have to be.

ATS 315: Working With Loops in C “for” loop syntax Sample loop that will run 5 times. main () { int i; for(i=0;i<5;i++) { printf (“%d\n”,i); }

ATS 315: Working With Loops in C “for” loop syntax On the first pass through the loop, i=0. main () { int i; for(i=0;i<5;i++) { printf (“%d\n”,i); }

ATS 315: Working With Loops in C “for” loop syntax “What the loop does” is inside a set of curly braces. main () { int i; for(i=0;i<5;i++) { printf (“%d\n”,i); }

ATS 315: Working With Loops in C “for” loop syntax Traditionally we indent the stuff inside a loop a little farther. main () { int i; for(i=0;i<5;i++) { printf (“%d\n”,i); }

ATS 315: Working With Loops in C “for” loop syntax After each pass through the loop, the “loop control variable” will be changed as shown here. main () { int i; for(i=0;i<5;i++) { printf (“%d\n”,i); }

ATS 315: Working With Loops in C “i++” ?!?!?!?!!!!??? i++ is a shortcut for “i=i+1” To increase in a different “step”, just be more explicit about it: i=i+2

ATS 315: Working With Loops in C “for” loop syntax As long as the loop control variable passes the “condition”, it will continue to loop. main () { int i; for(i=0;i<5;i++) { printf (“%d\n”,i); }

ATS 315: Working With Loops in C “for” loop syntax This loop will run 5 times: i=0,1,2,3,4 main () { int i; for(i=0;i<5;i++) { printf (“%d\n”,i); }

ATS 315: Working With Loops in C “for” loop syntax Traditional format: –There are three “arguments” in the for loop: for(i=0;i<n;i++) { }

ATS 315: Working With Loops in C “for” loop syntax Traditional format: –1. The starting value of the loop—usually zero. for(i=0;i<n;i++) { }

ATS 315: Working With Loops in C “for” loop syntax Traditional format: –2. The “condition” for the loop—it will run as long as this is true. for(i=0;i<n;i++) { }

ATS 315: Working With Loops in C “for” loop syntax Traditional format: –3. The “increment” of the loop—how to modify the value of the loop control variable. for(i=0;i<n;i++) { }

ATS 315: Working With Loops in C Floating Point Loops for(pressure=1000.0;pressure<1024.0; pressure=pressure+4.0) { }

ATS 315: Working With Loops in C Nested Loops One thing that could be inside of a loop is another loop. Excellent for working with grids of data…

ATS 315: Working With Loops in C Nested Loops for(i=0;i<5;i++) { for(j=0;j<3;j++) { printf (“%d %d\n”,i,j); }

ATS 315: Working With Loops in C The “while” Loop Is used when you don’t know in advance how many times the loop should run… it just needs to run “while” something is true.

ATS 315: Working With Loops in C “while” loop syntax Loop control variable needs to be “initialized”. tempF = 0.; while (tempF > -98.0) { printf (“Enter a temp in F to convert to C.\n”); printf (“Or enter -99 to end.\n”); scanf(“%f”,&tempF); tempC = (tempF-32.)*(5./9.); printf (“The temperature is %4.1fC.\n\n”); }

ATS 315: Working With Loops in C “while” loop syntax Loop will repeat “while” condition is true. tempF = 0.; while (tempF > -98.0) { printf (“Enter a temp in F to convert to C.\n”); printf (“Or enter -99 to end.\n”); scanf(“%f”,&tempF); tempC = (tempF-32.)*(5./9.); printf (“The temperature is %4.1fC.\n\n”); }

ATS 315: Working With Loops in C “while” loop syntax Loops are generally indented. tempF = 0.; while (tempF > -98.0) { printf (“Enter a temp in F to convert to C.\n”); printf (“Or enter -99 to end.\n”); scanf(“%f”,&tempF); tempC = (tempF-32.)*(5./9.); printf (“The temperature is %4.1fC.\n\n”); }

ATS 315: Working With Loops in C Uses of “while” “while” loops are generally used to trap errors.

ATS 315: Working With Loops in C Your Assignment Make a table of wind chill temperatures! 1.Prompt the user for an air temperature 2.Prompt the user for a lowest wind speed 3.Prompt the user for a highest wind speed 4.Prompt the user for an interval