Imperative programming organizes computation as orders given to a computer. A C program combines declarations, statements, function calls, and control structures to direct specific tasks. section 1.0 section 1.1
Listing 1.1 The first example of a C program
/* This may look like nonsense, but really is -*- mode: C -*- * 1 /
#include <stdlib.h> 2
#include <stdio.h>
3
/* The main thing that this program does. */ 4
int main(int argc, [[maybe_unused]] char* argv[argc+1]) {
// Declarations 5
double A[5] = { 6
[0] = 9.0, 7
[1] = 2.9,
[4] = 3.E+25, 8
[3] = .00007,
};
9
// Doing some work 10
for (size_t i = 0; i < 5; ++i) { 11
printf("element %zu is %g, \tits square is %g\n",
i,
A[i], 12
A[i]*A[i]); 13
}
14
return EXIT_SUCCESS; 15
}
The first C example declares an array, assigns selected elements, iterates with a for loop, calls printf, and returns success. section 1.0
Read the program from the inside out: printf is a function call with arguments, including a format string and computed expressions. The for statement repeatedly performs the output statement for each array element. section 1.1 section 1.0
printf("element %zu is %g, \tits square is %g\n",
i,
A[i],
A[i]*A[i]);
This excerpt isolates the imperative action: pass the index, an array value, and its square to printf. section 1.1
> ./getting-started element 0 is 9, its square is 81 element 1 is 2.9, its square is 8.41 element 2 is 0, its square is 0 element 3 is 7e-05, its square is 4.9e-09 element 4 is 3e+25, its square is 9e+50
Running the program produces five terminal lines, making the ordered computation visible through each element and its square. section 1.1
