Library routines

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Quick Questions

Shade in the A or B circle for each question.

1. What is a library routine?

A A ready-made subroutine supplied with the language

B A subroutine you must always write yourself

2. Which line calls a library routine?

A PROCEDURE ROUND(3.14159, 2)

B Result ← ROUND(3.14159, 2)

3. True or false: you have to write the code for ROUND yourself before using it.

A True

B False

4. Which is a benefit of using library routines?

A They save time and avoid errors because they are already tested

B They make the program run without needing any inputs

5. Which of these is a library routine from the IGCSE course?

A RANDOM()

B RETURNVALUE()

Match the Pairs

Draw a line connecting each item on the left to its match on the right.

Left column		Right column
1ROUND(3.14159, 2)		ARoll ← ROUND(RANDOM() * 5, 0) + 1
2LENGTH("Cambridge")		BMOD is missing its second value. A library routine such as MOD needs both values, for example 17 MOD 5, which gives 2.
3A library routine is called like a function, so its returned value can be stored in a variable		CA library routine call that returns 9, the number of characters in the string
4A library routine supplied with the language gives a random number without the programmer writing the code		DThe programmer wrote their own LENGTH routine and it does not work. LENGTH is already a library routine, so there is no need to write it.
5FUNCTION LENGTH(Word : STRING) RETURNS INTEGER RETURN 0 ENDFUNCTION		ETotal ← ROUND(Price * 1.2, 2)
6Answer ← 17 MOD		FA library routine call that returns 3.14, the number rounded to 2 decimal places

Definitions

library routine

Fill in the Blanks

Complete each line of code by filling in the missing parts.

Result ← _____(3.14159, 2)

OUTPUT ______("Cloodit")

Dice ← ROUND(______() * 6, 0)

Remainder ← 17 ___ 5

Whole ← 17 ___ 5

Spot the Error

Shade in the letter of the line that contains an error.

Question 1

A Word ← "computer"

B Size ← LENGTH Word

C OUTPUT Size

Question 2

A Rem ← MOD(17 5)

B OUTPUT Rem

C // Rem is 2

Question 3

A Pi ← ROUND(3.14159)

B OUTPUT Pi

C // Output is 3.14

Question 4

A DECLARE Chance : REAL

B Chance ← RANDOM()

C IF Chance > 5 THEN

D OUTPUT "Heads"

E ENDIF

Question 5

A Total ← 47

B Tens ← DIV(Total, 10)

C Units ← MOD(Total, 10)

D Check ← Tens + 10 + Units

E OUTPUT Check

Answer Key

Library routines

Section A: Quick Questions

A — A ready-made subroutine supplied with the language

B — Result ← ROUND(3.14159, 2)

B — False

A — They save time and avoid errors because they are already tested

A — RANDOM()

Section B: Match the Pairs

ROUND(3.14159, 2) → A library routine call that returns 3.14, the number rounded to 2 decimal places

LENGTH("Cambridge") → A library routine call that returns 9, the number of characters in the string

A library routine is called like a function, so its returned value can be stored in a variable → Total ← ROUND(Price * 1.2, 2)

A library routine supplied with the language gives a random number without the programmer writing the code → Roll ← ROUND(RANDOM() * 5, 0) + 1

FUNCTION LENGTH(Word : STRING) RETURNS INTEGER RETURN 0 ENDFUNCTION → The programmer wrote their own LENGTH routine and it does not work. LENGTH is already a library routine, so there is no need to write it.

Answer ← 17 MOD → MOD is missing its second value. A library routine such as MOD needs both values, for example 17 MOD 5, which gives 2.

Section C: Definitions

library routine — A ready-made subroutine supplied with the language that you can call without writing it, such as ROUND, RANDOM or LENGTH. It saves time and avoids errors.

Section D: Fill in the Blanks

Result ← ROUND(3.14159, 2)

OUTPUT LENGTH("Cloodit")

Dice ← ROUND(RANDOM() * 6, 0)

Remainder ← 17 MOD 5

Whole ← 17 DIV 5

Section E: Spot the Error

B — LENGTH is a library routine, so it is called like a function with the value in brackets. It should be Size ← LENGTH(Word).

A — The library routine MOD needs two values separated by a comma. It should be Rem ← MOD(17, 5).

A — ROUND needs two arguments: the value and the number of decimal places. It should be ROUND(3.14159, 2).

C — RANDOM() gives a number between 0 and 1, so it can never be greater than 5. The test should use a value such as 0.5.

D — To rebuild 47 from the DIV and MOD results, the tens must be multiplied by 10. It should be Tens * 10 + Units.