Example on how to divide c programm into multiple files

OneProgramInMultipleFiles/.gitignore

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+a.out
+

OneProgramInMultipleFiles/Makefile

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+#
+#simple makefile with only explicyt rules  
+#
+
+TARGET= a.out
+$(TARGET): main.o function1.o function2.o
+	gcc -o $(TARGET) main.o function1.o function2.o 
+
+main.o: main.c
+	gcc -c main.c
+
+function1.o: function1.c  function1.h 
+	gcc -c function1.c
+
+function2.o: function2.c  function2.h 
+	gcc -c function2.c
+

OneProgramInMultipleFiles/README.md

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+example how to create c program that uses more than one file
+
+compile with command :
+ gcc -Wall main.c function1.c function2.c
+
+or with command :
+ make
+

OneProgramInMultipleFiles/function1.c

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+#include "function1.h"
+
+int func1(int a, int b)
+{
+    return 2*(2*a+b);
+}
+

OneProgramInMultipleFiles/function1.h

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+#ifndef FUNCTION1_H
+#define FUNCTION1_H
+
+int func1(int a, int b);
+
+#endif
+

OneProgramInMultipleFiles/function2.c

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+#include "function2.h"
+
+int func2(int a, int b)
+{
+    return a-2-1*3*b;
+}
+

OneProgramInMultipleFiles/function2.h

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+#ifndef FUNCTION2_H
+#define FUNCTION2_H
+
+int func2(int a, int b);
+
+#endif
+

OneProgramInMultipleFiles/main.c

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+#include <stdio.h>
+#include "function1.h"
+#include "function2.h"
+
+int main(void)
+{
+    int a, b;
+    printf("Insert two numbers: ");
+    if(scanf("%d %d", &a, &b)!=2)
+    {
+        fputs("Invalid input", stderr);
+        return 1;
+    }
+    printf("func1 result: %d\n", func1(a, b));
+    printf("func2 result: %d\n", func2(a, b));
+    return 0;
+}
+