Cheatography

# Algorithm IGCSE Cheat Sheet by [deleted]

This is a cheat sheet for pseudocode in Computer Science IGCSE ~

### Data Types & Structures

 INTEGER (whole numbers) 1, 2, 45, 231, -2, -213 REAL (decimal numbers) 1.23, 938.23­2312, -23.233 STRING (words or sentences) “Hello World”, “123 bipbop” CHARACTER (one character or alphabet) ‘A’, ‘b’, ‘Y’, ‘o’, ‘1’, ‘8’, ‘d BOOLEAN (true or false) TRUE, FALSE, TRUE, TRUE ARRAY (many words or numbers) [“Hi”, “me not smart”, 174, 23, “12 bipbop”, -1234]
Rules:
INT and REAL are typed as numbers only
STR must be in double quotation marks i.e. "­Hel­lo"
CHAR must be in single quotation marks i.e. 'H'
BOOL must be in either TRUE or FALSE
Array can be assigned to variables and must be inside braces. i.e. names = ["An­dy", "­Cin­dy", "­Bob­by"]

### Operators (Arith­metic)

 Operators Examples It Will Give + (plus) 5 + 5 10 - (minus) 8 - 3 5 * (multiply) 6*2 12 / (divide) 8/4 2 ^ (power) 2^3 8 DIV (dividend) 12 DIV 5 2 MOD (modulo) 10 MOD 5 0
Note: MOD will give you the remainder of the number

### Operators (Assig­nment)

 Operators Examples > (greater than sign) 100 > 5 < (lesser than sign) 60 < 150 <> (not equal sign) 7 <> 25 = (equal sign) 12 = 12
The >= operator means greater than or equal to
The <= operator means lesser than or equal to

### Operators (boolean)

 Operators Examples AND TRUE AND TRUE = TRUE OR TRUE OR FALSE = TRUE NOT NOT FALSE = TRUE
Boolean Operators are also called Logical Operators. AND means conjun­ction, OR means disjun­ction, NOT means negation

### The FOR Loop

 ``````FOR LOOP Use a FOR loop when you know how many times it'll run      The syntax: FOR variable = something to something     do something NEXT The example: FOR number = 1 to 3:     PRINT number NEXT``````
Running this on raptor/ other engines will output:
1
2
3

### REPEAT Loop

 ``````THE REPEAT LOOP Use a REPEAT loop when you know how many times it'll run The syntax: REPEAT     do something UNTIL something The example: number = 1 REPEAT     PRINT number     number = number + 1 UNTIL number = 3``````
Running this on raptor/ other engines will output:
1
2
3

### WHILE Loop

 ``````THE WHILE LOOP Use WHILE loop when you don't know how many times it'll run The syntax: WHILE something DO     do something ENDWHILE The example: number = 1 WHILE number < 3 DO     PRINT number     number = number + 1 ENDWHILE``````
If you put this in raptor­/other engines they will output:
1
2
3

### Writing An Algorithm Example

 You are tasked to find out what is the 16th number in the Fibonacci sequence, how do you do it? ``fib_0 = 0````fib_1 = 1````find_num = 16````FOR i = 0 to find_num````___ fib_2 = fib_0 + fib_1````___ fib_0 = fib_1````___ fib_1 = fib_2````PRINT "The 16th number is: ", fib_2`` Answer of Output = 987
Fibonacci Sequence is a sequence where each number is the sum of the two preceding ones. For example: 0, 1, 1, 2, 3, 5, 8, 13, 21, 34

### Condit­ional Statements (IF)

 ``````Syntax: IF condition     THEN do something     ELSE do something else ENDIF Example: khaisar_height = 100 IF khaisar_height < 120     THEN PRINT “Please enter the kids room”     ELSE PRINT “Please enter the teenagers room” ENDIF``````
Descri­ption:
Condit­ional Statements are IF statem­ents. The IF statement check if a condition is TRUE or FALSE.

In the English language, we say:
If you come to the party, I'll buy one pizza.

In the computer language. We say it like this:
IF answer = “YES” THEN pizza = 1 ENDIF
As simple as that!

### Extended IF statement

 ``````IF grade > 90 AND behavior > 80     THEN PRINT "Excellent" ELIF grade > 80 AND behavior > 70     THEN PRINT "Well Done" ELIF grade > 70 AND behavior > 60     THEN PRINT "Good Job" ELSE PRINT "Improvement is needed!" ENDIF``````
IF and ELIF (else if) are used for a choice between several different values. You can either use ELIF or CASE, it is up to you.

### CASE OF

 ``````Syntax: CASE ... OF     something     OTHERWISE something ENDCASE Example: CASE grade OF     'A' : PRINT "Excellent"     'B' : PRINT "Well Done"     'C' : PRINT "Good Job"     'D' : PRINT "Do Better"     'F' : PRINT "Find Another Answer"     OTHERWISE PRINT "Improve next time" ENDCASE``````
CASE is another condit­ional statement that is use for several different values

### Functions

 ``````The syntax: FUNCTION do_something(Parameters)     statements     RETURN something END PROCEDURE Example: FUNCTION count_pizza_slices(number_of_pizza)     number_of_pizza_slices = 0     number_of_pizza_slices = number_of_pizza * 8     RETURN number_of_pizza_slices END PROCEDURE``````
Running this on a engine­/idle:
count_­piz­za_­sli­ces(5)

Output:
40