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Mar 9th, 2005

C++ BASICS ==> Pointers, Call by Reference/Value, Inheritance, Functions & Arrays

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In my old C++ programming classes I would often trip up on theses basic concepts when things got more and more complicated:

1. Arrays
2. Functions
3. Inheritance
4. Call by Reference
5. Call by Value
6. Pointers

I kind of know how they work but don't really know what they are good for in real life applications. Could somebody explain his or her:

(A) Definition of the concept
(B) Understanding of what the concept does/how it works
(B) Quick example of the concepts use in real life applications (i.e. what is it good for?)

I'll put my understandings and explanation up later tonight, tomorrow the latest

Fasola

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Mar 9th, 2005

Re: C++ BASICS ==> Pointers, Call by Reference/Value, Inheritance, Functions & Arrays

Each of these are rather broad topics. Can you cut it down to specific questions so we don't have to write page after page of tutorials?

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Mar 9th, 2005

Re: C++ BASICS ==> Pointers, Call by Reference/Value, Inheritance, Functions & Arrays

Quote originally posted by Narue ...

Each of these are rather broad topics. Can you cut it down to specific questions so we don't have to write page after page of tutorials?

Okay, lets deal with functions first, then inheritance

lets start with the format of a function:

return-value-type function name( parameter-list)
{
declaractions and statements
}

^^^what does all that mean, and what does it mean whem you have nothing in the parameter-list compared to when you do have something(s) in the parameter-list?

that one always gets me

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Re: C++ BASICS ==> Pointers, Call by Reference/Value, Inheritance, Functions & Arrays

return-value-type Any value, or none at all, that you want to return from the function: an error code, a calculated result, etc.

parameter-list Any value(s) -- or possibly references in C++, or none at all, that you want to pass to the function: a pointer to an array to calculate the sum, for example.

declaractions and statements The "meat"; what it takes to do whatever it is the function does.

what does it mean whem you have nothing in the parameter-list compared to when you do have something(s) in the parameter-list?

It means whatever you want it to mean. This is a little like asking how a painter turns paints and canvas into a portrait.

Dave Sinkula

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Re: C++ BASICS ==> Pointers, Call by Reference/Value, Inheritance, Functions & Arrays

Quote originally posted by Dave Sinkula ...

parameter-list Any value(s) -- or possibly references in C++, or none at all, that you want to pass to the function

okay you touched on something there! what do you mean by "pass to the function"

explain with an example please

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Re: C++ BASICS ==> Pointers, Call by Reference/Value, Inheritance, Functions & Arrays

C++ Syntax (Toggle Plain Text)
#include <stdio.h>
 
int multiply(int x, int y)
{
   return x * y;
}
 
int main()
{
   int result = multiply(2,3);
   printf("result = %d\n", result);
   return 0;
}
 
/* my output
result = 6
*/
#include <stdio.h>

int multiply(int x, int y)
{
   return x * y;
}

int main()
{
   int result = multiply(2,3);
   printf("result = %d\n", result);
   return 0;
}

/* my output
result = 6
*/

C++ Syntax (Toggle Plain Text)
#include <stdio.h>
 
int multiply(int x, int y)
{
   return x * y;
}
 
int main()
{
   int i, j;
   for (i = 1; i < 10; ++i)
   {
      for (j = 1; j < 10; ++j)
      {
         printf("%2d ", multiply(i, j));
      }
      putchar('\n');
   }
   return 0;
}
 
/* my output
 1  2  3  4  5  6  7  8  9 
 2  4  6  8 10 12 14 16 18 
 3  6  9 12 15 18 21 24 27 
 4  8 12 16 20 24 28 32 36 
 5 10 15 20 25 30 35 40 45 
 6 12 18 24 30 36 42 48 54 
 7 14 21 28 35 42 49 56 63 
 8 16 24 32 40 48 56 64 72 
 9 18 27 36 45 54 63 72 81 
*/
#include <stdio.h>

int multiply(int x, int y)
{
   return x * y;
}

int main()
{
   int i, j;
   for (i = 1; i < 10; ++i)
   {
      for (j = 1; j < 10; ++j)
      {
         printf("%2d ", multiply(i, j));
      }
      putchar('\n');
   }
   return 0;
}

/* my output
 1  2  3  4  5  6  7  8  9 
 2  4  6  8 10 12 14 16 18 
 3  6  9 12 15 18 21 24 27 
 4  8 12 16 20 24 28 32 36 
 5 10 15 20 25 30 35 40 45 
 6 12 18 24 30 36 42 48 54 
 7 14 21 28 35 42 49 56 63 
 8 16 24 32 40 48 56 64 72 
 9 18 27 36 45 54 63 72 81 
*/

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Mar 10th, 2005

Re: C++ BASICS ==> Pointers, Call by Reference/Value, Inheritance, Functions & Arrays

Quote originally posted by Dave Sinkula ...

C++ Syntax (Toggle Plain Text)
#include <stdio.h>
 
int multiply(int x, int y)
{
   return x * y;
}
 
int main()
{
   int result = multiply(2,3);
   printf("result = %d\n", result);
   return 0;
}
 
/* my output
result = 6
*/
#include <stdio.h> int multiply(int x, int y) { return x * y; } int main() { int result = multiply(2,3); printf("result = %d\n", result); return 0; } /* my output result = 6 */

hmmm...thanx for the break down...ok so did you pass parameters x and y in function multiply() to function multiply() found in the function main()? am i right or wrong?

and what is this "%d", what does it do?

please explain whats going on in the printf() function

Quote originally posted by Dave Sinkula ...

C++ Syntax (Toggle Plain Text)
#include <stdio.h>
 
int multiply(int x, int y)
{
   return x * y;
}
 
int main()
{
   int i, j;
   for (i = 1; i < 10; ++i)
   {
      for (j = 1; j < 10; ++j)
      {
         printf("%2d ", multiply(i, j));
      }
      putchar('\n');
   }
   return 0;
}
 
/* my output
 1  2  3  4  5  6  7  8  9 
 2  4  6  8 10 12 14 16 18 
 3  6  9 12 15 18 21 24 27 
 4  8 12 16 20 24 28 32 36 
 5 10 15 20 25 30 35 40 45 
 6 12 18 24 30 36 42 48 54 
 7 14 21 28 35 42 49 56 63 
 8 16 24 32 40 48 56 64 72 
 9 18 27 36 45 54 63 72 81 
*/
#include <stdio.h> int multiply(int x, int y) { return x * y; } int main() { int i, j; for (i = 1; i < 10; ++i) { for (j = 1; j < 10; ++j) { printf("%2d ", multiply(i, j)); } putchar('\n'); } return 0; } /* my output 1 2 3 4 5 6 7 8 9 2 4 6 8 10 12 14 16 18 3 6 9 12 15 18 21 24 27 4 8 12 16 20 24 28 32 36 5 10 15 20 25 30 35 40 45 6 12 18 24 30 36 42 48 54 7 14 21 28 35 42 49 56 63 8 16 24 32 40 48 56 64 72 9 18 27 36 45 54 63 72 81 */

Hmmmmm....in the function multiply() how did you go from parameters x and y to i and j, that looks like a "call-by-reference" but i don't understand why you did that and how it works, please explain dave

and what does the function putchar() mean

Fasola

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Mar 10th, 2005