Functions in Objective-C and C Programming

Paul Solt iPhoneDev.tv

FunctionsInstruction manuals for computers


Outline•Functions

•Stack Frame

•Recursion

•Debugging

•Global Variables


Desk

1. Build small drawer2. Build large drawer 3. Build desk frame4. Insert small drawer5. Insert large drawer


Area = A x B

Area

A

B


int area(int sideA, int sideB)



return type



name

return type



name parameter

return type

parameter


int area(int sideA, int sideB) { int result = sideA * sideB; return result; }


int total = area(4, 2);



arguments



8

arguments


Stack Frame

•“Sandbox”

•Local Variables


Stack Frame

•“Sandbox”

•Local Variables

main()total = area(4,2);


Stack Frame

•“Sandbox”

•Local Variables


area(4,2)sideA = 4sideB = 2result = 8


Stack Frame

•“Sandbox”

•Local Variables



Stack Frame

•“Sandbox”

•Local Variables

main()total = 8;


Stack Frame

•“Sandbox”

•Local Variables


Area


Recursion

Space Shuttle: Countdown Timer1. Display number2. Subtract one3. Repeat steps 1 and 2 (until 0) STS-110, NASA


Recursion


Recursionvoid countDown(int number) { if(number == 0) { printf("Take off!\n"); } else { printf("T-minus %d seconds\n", number); int nextNumber = number - 1; countDown(nextNumber); }}


Stack Frame


Stack Framemain()startNumber = 5countDown(5)


Stack Framemain()startNumber = 5countDown(5)countDown(5)nextNumber = 4countDown(4)


Stack Framemain()startNumber = 5countDown(5)countDown(5)nextNumber = 4countDown(4)countDown(4)nextNumber = 3countDown(3)


Stack Framemain()startNumber = 5countDown(5)countDown(5)nextNumber = 4countDown(4)countDown(4)nextNumber = 3countDown(3)countDown(3)nextNumber = 2countDown(2)


Stack Framemain()startNumber = 5countDown(5)countDown(5)nextNumber = 4countDown(4)countDown(4)nextNumber = 3countDown(3)countDown(3)nextNumber = 2countDown(2)countDown(2)nextNumber = 1countDown(1)


Stack Framemain()startNumber = 5countDown(5)countDown(5)nextNumber = 4countDown(4)countDown(4)nextNumber = 3countDown(3)countDown(3)nextNumber = 2countDown(2)countDown(2)nextNumber = 1countDown(1)countDown(1)nextNumber = 0countDown(0)


Stack Framemain()startNumber = 5countDown(5)countDown(5)nextNumber = 4countDown(4)countDown(4)nextNumber = 3countDown(3)countDown(3)nextNumber = 2countDown(2)countDown(2)nextNumber = 1countDown(1)countDown(1)nextNumber = 0countDown(0)countDown(0)take off!


Stack Framemain()startNumber = 5countDown(5)countDown(5)nextNumber = 4countDown(4)countDown(4)nextNumber = 3countDown(3)countDown(3)nextNumber = 2countDown(2)countDown(2)nextNumber = 1countDown(1)countDown(1)nextNumber = 0countDown(0)


Stack Framemain()startNumber = 5countDown(5)countDown(5)nextNumber = 4countDown(4)countDown(4)nextNumber = 3countDown(3)countDown(3)nextNumber = 2countDown(2)countDown(2)nextNumber = 1countDown(1)


Stack Framemain()startNumber = 5countDown(5)countDown(5)nextNumber = 4countDown(4)countDown(4)nextNumber = 3countDown(3)countDown(3)nextNumber = 2countDown(2)


Stack Framemain()startNumber = 5countDown(5)countDown(5)nextNumber = 4countDown(4)countDown(4)nextNumber = 3countDown(3)


Stack Framemain()startNumber = 5countDown(5)countDown(5)nextNumber = 4countDown(4)


Stack Framemain()startNumber = 5countDown(5)


Stack Frame


CountDown!


Global Variablesint total = 10

resetTotal()total = 0;

updateTotal()total = total + 1;


Global Variables


Review•Functions

•Stack Frame

•Recursion

•Debugging

•Global Variables

Functions in Objective-C and C Programming

Education

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