Pseudocode (unit 8)

Question 1

Rule for keywords

Answer 1

Must be capital

Question 2

How to show comments

Answer 2

//

Question 3

State 5 data types + how are they written/delimited

Answer 3

1. INTEGER = whole number
2. REAL = number capable of containing a fractional part. At least 1 number on both sides of decimal point.
3. CHARACTER = a single character. Written using single brackets ‘ ‘
4. STRING = a sequence of characters. Written using double brackets “ “
5. BOOLEAN = logic values true and false

Question 4

Identifiers

Answer 4

Names given to variables, constants, procedures & functions. Letters and digits only.

Question 5

Declaration

Answer 5

States/declares data type of variable (by its identifier).
DECLARE [identifier] : [data type]

Question 6

Constant

Answer 6

A value in a program that never changes.

Question 7

Assignment operator

Answer 7

<— (arrow)
Format: identifier <— value

Question 8

Array + declaration (1d & 2d)

Answer 8

Fixed-length structure of elements of identical data types, accessible using index numbers. E.g. ArrayName[Index] <— 23
1d: DECLARE identifier : ARRAY[1:30] OF data type
2d: DECLARE identifier : ARRAY[1:30, 1:30] OF data type

Question 9

Input and output operations

Answer 9

INPUT identifier
OUTPUT values or “string”

Question 10

Not standard arithmetic operations

Answer 10

^ = to the power of
DIV(x,y) = returns quotient/whole number left after division of x by y
MOD(x,y) = returns remainder after division of x by y

Question 11

Not equal to symbol

Answer 11

<>

Question 12

4 string operations

Answer 12

1. LENGTH(identifier) = length of string
2. LCASE(identifier) = returns string/character in lowercase
3. UCASE(identifier) = returns string/character in uppercase
4. SUBSTRING(identifier, start, length) = returns string of length length from position start. In pseudo code, first position is usually 1.

Question 13

Round & random library routines

Answer 13

1. ROUND(identifier, places) = returns value rounded to places d.p
2. RANDOM() = returns random number between 0 and 1 (inclusive)

Question 14

Selection

Answer 14

IF condition:
THEN
statements
ELSE
statements
ENDIF
(THEN can be placed in same line as IF, and ELSE is not needed. ELIF can be used)

Question 15

State & explain 3 types of loops

Answer 15

1. Count-controlled loop = for loop. Repeats loop/program set number of times.
2. Post-condition loop = REPEAT…until loops. Repeats loop until a condition is true. Executed at least once.
3. Pre-condition loop = while…do loop. Repeats loop while a condition is true. Tested before statements, and is only executed if condition evaluates to True. May run 0 times if condition is false beforehand.

Question 16

Variable

Answer 16

Data structure used to store value in a program that can change/be overwritten any number of times.

Question 17

For loop structure

Answer 17

FOR identifier <— value1 to value2:
statements
NEXT identifier

Question 18

Repeat loop structure

Answer 18

REPEAT
statements
UNTIL condition

Question 19

While loop structure

Answer 19

WHILE condition DO
statements
ENDWHILE

Question 20

Subroutines

Answer 20

Functions & procedures. Blocks of associated code/subroutines (separated piece of named code that performs a particular task) that can be called multiple times.

Question 21

Parameter + purpose

Answer 21

Value that adds extra information to a subroutine to adjust its behavior.
Alows procedure to be reused with different data/values.

Question 22

Procedure structure

Answer 22

Does not return value.
PROCEDURE identifier (parameter:datatype)
statements
ENDPROCEDURE
To call:
CALL identifier

Question 23

Function

Answer 23

= additional parameters can be added, in order to specify what variables the function is operating on

Return a single value to the point at which they are called.
FUNCTION identifier (p) RETURNS data type
RETURN statements
ENDFUNCTION
Cannot be called, would use it in output/print statement
p = possible parameters

Question 24

File handling

Answer 24

OPENFILE “file identifier.txt” FOR file mode
statement
CLOSEFILE ‘file identifier.txt’
File mode can be READ or WRITE (new file will be created & any existing data in the file will be lost)
Statement can be:
1. READFILE ‘identifier.txt’, variable - data from file will be read from text file into variable
2. WRITEFILE ‘identifier.txt’, variable - data from variable is written into file.

Question 25

Write an example for loop printing all elements in array in pseudo code

Answer 25

array <-- [] for i <-- 1 to y (length/number of times you iterate): OUTPUT array[i] NEXT i

Question 26

State 4 ways to write program so that it can be maintained/understood by other programmers + explanation

Answer 26

1. Use comments to explain purpose of different sections of algorithm, e.g. logic or syntax 2. Use meaningful identifiers for variables that clearly explain their purpose, e.g. what it stores 3. Use prodecures & functions to avoid repeating code + to simplify it 4. Use indentation & white space to make program more readable

Question 27

CASE statement

Answer 27

Allow one of several branches to be executed depending on value of variable. INPUT identifier CASE OF identifier value1 : statement value2 : statement OTHERWISE : statement ENDCASE

Question 28

The function Odds(X) returns ‘Odd’ if the value of X is an odd number and returns ‘Even’ if the value of X is an even number. Write pseudocode statements to: * define the function * call the function using parameter A and store the return item in variable B (explain this)

Answer 28

FUNCTION Odds(X:INTEGER) RETURNS STRING IF MOD(X,2) = 0 THEN RETURN "Even" ELSE RETURN "Odd" ENDIF ENDFUNCTION Calling: B <- Odds(A) This means that the value of A (which is a parameter that is specified earlier) is put into X and undegos the process inside the function. The result (Even or Odd) is then assigned to the variable B.

Question 29

Why is it useful to store data in a file?

Answer 29

Data stored in a file is a permanent copy which prevents it from being lost, so it can be used again in other programs. It can also be easily transferred to another computer like this.