Algorithms (Cambridge (CIE) IGCSE Computer Science)

Describe the purpose of the algorithm.

The variables X, Y and Z are used to store data in a program:

• X stores a string

• Y stores a position in the string (e.g. 2)

• Z stores the number of characters in the string.

The function LENGTH(X) finds the length of a string X.

The function SUBSTRING(X,Y,Z) finds a substring of X starting at position Y and Z characters long. The first character in X is in position 1.

Write pseudocode statements to:

• store the string "Programming is fun" in X

• find the length of the string and output it

• extract the word fun from the string and output it.

The one-dimensional (1D) array StudentName[] contains the names of students in a class. The two-dimensional (2D) array StudentMark[] contains the mark for each subject, for each student. The position of each student’s data in the two arrays is the same, for example, the student in position 10 in StudentName[] and StudentMark[] is the same.

The variable ClassSize contains the number of students in the class. The variable SubjectNo contains the number of subjects studied. All students study the same number of subjects.

The arrays and variables have already been set up and the data stored.

Students are awarded a grade based on their average mark.

Write a program that meets the following requirements:

• calculates the combined total mark for each student for all their subjects

• calculates the average mark for each student for all their subjects, rounded to the nearest whole number

• outputs for each student:

  • name

  • combined total mark

  • average mark

  • grade awarded

• calculates, stores and outputs the number of distinctions, merits, passes and fails for the whole class.

You must use pseudocode or program code and add comments to explain how your code works.

You do not need to initialise the data in the array.

Draw a flowchart for an algorithm to:

• allow numbers to be input

• ignore any numbers that are negative

• count how many numbers are positive

• output the count of positive numbers when zero is input and end the algorithm.

Explain the changes you will make to your algorithm to also count the negative numbers.

A function LENGTH(X) finds the length of a string X and a function SUBSTRING(X,Y,Z) finds a substring of X starting at position Y and Z characters long. The first character in the string is position 1.

Show the value of the variable after each pseudocode statement has been executed.

01 P ← "Computer Science" .............................................................

02 Q ← LENGTH(P) ..................................................... ........................

03 R ← SUBSTRING(P,10,7) .............................................................

04 S ← LENGTH(R) ......................................................................... ..

05 T ← SUBSTRING(R,1,3) .................................................................

Rewrite this pseudocode algorithm using a WHILE … DO … ENDWHILE loop.

B ← FALSE
INPUT Num
FOR Counter ← 1 TO 12
IF A[Counter] = Num
THEN
B ← TRUE
ENDIF
NEXT Counter

The names of patients are stored in the one-dimensional (1D) array Patient[] of type string. A separate two-dimensional (2D) array Readings[] stores the latest data recorded about each patient. The array already contains the readings taken by a nurse for each patient:

• temperature measured to one decimal place

• pulse rate, a whole number.

Temperature readings should be in the range 31.6 to 37.2 inclusive.
Pulse readings should be in the range 55.0 to 100.0 inclusive.

The hospital number given to the patient is used for the index on both arrays, this is a value between 1 and 1000 inclusive.

When the data for a patient is checked a warning is given if any of the readings are out of range.
If both readings are out of range, then a severe warning is given.

Write a procedure, using pseudocode or program code, that meets the following requirements:

• takes the hospital number as a parameter

• checks if the number is valid

• outputs an error message and exits the procedure if the number is not valid

• if the hospital number is valid:

  • output the patient’s name

  • output ‘Normal readings’ if both the readings are within range

  • output ‘Warning’ and the name of the reading e.g. ‘Pulse’ if one reading is out of range

  • output ‘Severe warning’ and the names of the two readings ‘Pulse and temperature’ if both readings are out of range

  • exits the procedure.

You must use pseudocode or program code and add comments to explain how your code works.

You do not need to initialise the data in the arrays.

An algorithm has been written in pseudocode to allow some numbers to be input. All the positive numbers that are input are totalled and this total is output at the end. An input of 0 stops the algorithm.

01 Exit  1
02 WHILE Exit <> 0 DO
03   INPUT Number
04   IF Number > 0
05     THEN
06       Total Total + Number
07     ELSE
08       IF Number = 0
09         THEN
10           Exit  0
11       ENDIF
12   ENDIF
13 ENDWHILE
14 OUTPUT "The total value of your numbers is ", Total 

Describe how you could change the corrected algorithm to record and output how many positive numbers have been included in the final total.

You do not need to rewrite the algorithm.