Give an example of a count controlled loop structure, explain how you determine

Question

Give an example of a count controlled loop structure, explain how you determine the number of times it will execute its body. How will you determine the number of times a conditional controlled loop with a sample input set executes its body?

Explanation / Answer

The LOOP structure is used to repeatedly execute a group of statements. It has three different forms, the simplest being as follows: LOOP statements END LOOP This form sets up an infinite loop, but an additional statement, BREAK, may be used to terminate the loop. BREAK would, of course, normally have to be inside an IF structure. PROC COUNT { A procedure to print the numbers from 1 to 10 } I = 1 LOOP PRINT (I) I = I+1 IF I > 10 BREAK ENDIF ENDLOOP ENDPROC As it is frequently required to loop over a sequential range of numbers in this way, a special form of the LOOP statement is provided for this purpose. It has the following form: LOOP FOR variable = expression1 TO expression2 [ STEP expression3 ] statements END LOOP This form is essentially equivalent to the DO loop in FORTRAN. The expressions specifying the range of values for the control variable are rounded to the nearest integer so that the variable always has integer values. Using this form of the LOOP statement we can simplify the previous example as follows: PROC COUNT { A procedure to print the numbers from 1 to 10 } LOOP FOR I = 1 TO 10 PRINT (I) ENDLOOP ENDPROC Note that there is an optional STEP clause in the LOOP FOR statement. If this is not specified a STEP of 1 is assumed. The STEP clause can be used to specify a different value. A step of -1 must be specified to get a loop which counts down from a high value to a lower value. For example: LOOP FOR I = 10 TO 1 STEP -1 will count down from 10 to 1. The third form of the LOOP structure allows the setting up of loops which terminate on any general condition. It has the form: LOOP WHILE expression statements END LOOP The expression is evaluated each time round the loop, and if it has the logical value TRUE the statements which form the body of the loop are executed. If it has the value FALSE execution continues with the statement following END LOOP. Using this form we can write yet another version of the COUNT procedure: PROC COUNT { A procedure to print the numbers from 1 to 10 } I = 1 LOOP WHILE I

Related Questions

Navigate

• Browse (All)
• Browse G
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.