Reusing of Variable and memory concept in C

Question

If I declare a variable as - extern int c; // I can reuse this variable in another function and no memory is allocated to it.

If I initialize a variable as - uint32 a[32]; // 32*4 bytes of memory is allocated.how to to reuse the above variable in another program ? Example : I am using a pointer to access the value or address of it.

MAIN.c : extern uint32 a[32]; and try to reuse it in a another program as i — user2984410, Nov 29 '13 at 07:33
What do you mean by "another program"? Do you mean like [shared memory](http://en.wikipedia.org/wiki/Shared_memory) between processes? — Some programmer dude, Nov 29 '13 at 07:36
If you get compiler or linker errors, please edit your question to include them (complete and unedited). Also please edit your question to show a complete code example (also known as a [SSCCE](http://sscce.org/)). You should probably also read [the Stack Overflow question checklist](http://meta.stackexchange.com/questions/156810/stack-overflow-question-checklist), it will help you write better questions in the future. — Some programmer dude, Nov 29 '13 at 07:44

score 1 · Answer 1 · edited May 23 '17 at 12:28

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Use extern only when you have multiple source files. An extern variable is a declaration of a variable which is defined in another translation unit. Compiler allocates storage when the variable is defined

Refer to THIS POST ON SO for more information

edited May 23 '17 at 12:28

Community

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answered Nov 29 '13 at 07:41

pratim_b

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MAIN.h : extern int a; ONE.c : int a[32]; TWO.c : int *p; p=&a; // I will include MAIN.h in both ONE and TWO program. why isn't working ?? – user2984410 Nov 29 '13 at 07:50
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int a and int a[] are different. One is array. Change your extern to extern int a[32]; – pratim_b Nov 29 '13 at 07:52
MAIN.h : extern int a[32]; ONE.c : int a[32]; TWO.c : int *p; p=&a; // why it's not working ?? I am including .h file in both program. – user2984410 Nov 29 '13 at 07:59
Compile using gcc ONE.c TWO.c -o main – pratim_b Nov 29 '13 at 08:05
I am using visio c++ as IDE. – user2984410 Nov 29 '13 at 08:09
Error c2061: identifier 'a' error C2059: syntax error : syntax error ';' Error c3409: empty attribute block is not allowed – user2984410 Nov 29 '13 at 08:15
I solved it : I forgot to put typedef unsigned _int32 uint32 ; – user2984410 Nov 29 '13 at 08:20

Reusing of Variable and memory concept in C

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