CMSC104

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Lecture 16: For Loops

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Reading Assigned:   5.4 - 5.8

Homework Due:  Homework 07

Homework Assigned:  Homework 08

Classwork Assigned:  Classwork 09

Topics Covered:

• Homework 7 Solution and Solution with extra credit
• Homework X Solution
• For loops
  • For loops are the third type of loops used in C
  • For loops consist of the following syntactical elements
  • for ( INIT; TEST; INCREMENT) { code; }
  • INIT, TEST, and INCREMENT are normally expressions
  • INIT normally takes the form "x = 0;"
  • The INIT expression is only executed prior to the loop beginning
  • TEST normally takes the form "x < 10;"
  • The TEST expression is checked, and the code is only executed if TEST is true
  • The TEST expression must be true even the first time the loop tries to run
  • INCREMENT normally takes the form "x = x + 1"
  • The INCREMENT expression is executed at the end of each run through the loop
  • A for loop of the form:

    int x;
    for(x=0; x<10; x=x+1) {
      printf("x is %d\n", x);
    }
    

  • can be rewritten as a while loop like this:

    int x;
    x=0;
    while(x<10) {
      printf("x is %d\n", x);
      x=x+1;
    }
    

• Increment and decrement
  • One additional syntax often used with for loops are the increment and decrement operators
  • Increment operators take the form x++;
  • This code has the same effect as x = x + 1;
  • Decrement operator -- is the inverse operator, it will subtract one from the left hand side
  • Increment and decrement operators are often used as the INCREMENT portion of for loops