Programming Concepts GapFill

Once you have decided on an algorithm to solve a problem, it is useful to think about the programming constructs that you will need to use.

For example, in this algorithm:

Step 1: Get user input
Step 2: Ask the user if they would like to make a substring from their input
Step 3: If they say yes, ask them for the start position and length of their desired substring
Step 4: Set the value of the input to be the substring specified by the user
Step 5: Repeat the previous three steps until the user says no
Step 6: Output the final value of the input

We can see from   Step 1Step 4Step 2Step 3 above that the algorithm will require some sort of selection. We can see from   Step 5Step 1Step 3Step 2 that it will also require iteration.

To start programming the algorithm, we should start from the first step and follow each step through in order. First, we get input from the user:

PRINT('Enter a word or phrase')

userString  ← USERINPUTstr= INPUTchar

 responseanswerresultstring = ''

The response of the user input is stored as   a constanta variablean assignmentan operator so that it can be used and edited later. We then move on to the next step, asking the user if they would like to make a substring from their input:

PRINT('Would you like to make a substring of '+ userString + (y/n)')

response ← USERINPUT

The next two steps depend on the result of the entry so we need a   functioniterationselectionsequence statement:

     PRINT('Would you like to make a substring of '+ userString + (y/n)')

     response ← USERINPUT

     IF  stringentryinputresponse ='y' THEN

           PRINT('Enter the start position of your new substring')

           subStrStart ← USERINPUT

           PRINT('Enter the end position of your new substring')

           subStrEnd ← USERINPUT

           userString ←  SUBSTRING(subStrStart,subStrEnd,userString)substring(subStrEnd, subStrStart)userString(sub,StrStart,StrEnd)userString.start.end(substring)

 if endENDIFendbreak

We now need to make the program loop through the necessary steps:

WHILE response  >====!= 'n'   

     ...

 finishfinish whilewhile endENDWHILE

Finally, we output the result:

 print(‘userString’)print USERSTRINGprint “userString”PRINT(userString)