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Passing a reference to allow a variable to be change from a function
Pointers and references example from a Well House Consultants training course
More on Pointers and references [link]
Source code: p2.c Module: C207
#include <stdio.h>
/* When we call a function, we pass in values to be used / referenced as copies under a different variable name within the function; by copying a value, there's no danger of the function unexpectedly changing it, and by using a new name, which is isoloated to the function, we're hiding within (encapsulating) that name within that function and avoiding too many problems with conflicting names as the program grows. However ... if we copy in a value, we're removing the option which we sometimes need of changing the original in the calling code which we sometimes want - if (for example) we're reading in data and wish to store it in a named variable. We can provide a read/write capability to a variable in the calling function by passing a pointer to it (its address / a reference) into the function */ tolegs (int * many) { *many *= 2; } main () { int peeps; /* Passing in references allows us to amend contents */ scanf("%d",&peeps); tolegs(&peeps); /* Passing in values copies the values and makes them safe from amendment from within the called routine */ printf("Legses is %d\n",peeps); } /* Sample output: munchkin:c2 grahamellis$ ./p2 Legses is 12 munchkin:c2 grahamellis$ */ Learn about this subject
This module and example are covered on the following public courses:
* Learning to Program in C * Learning to program in C and C++ * Programming in C * C and C++ Programming * Learning to program in C and C++ * C and C++ Programming Also available on on site courses for larger groups Books covering this topic
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