In C how is this parameter declared in the function? -

i trying learn basics of c using the c programming language - brian kernighan , dennis ritchie

in program below, don't understand value 'maxlinelength' comes from?

the loop set run while 'i' smaller maxlinelength-1, value of maxlinelength , come from?

from understand, when parameters declared in function value being passed them, must surely declared somewhere else have value passed in?

#include <stdio.h> #define maximumlinelength 1000 #define longline 20  main() {  int stringlength;  char line[maximumlinelength];    while((stringlength = getlinelength(line, maximumlinelength)) > 0)     if(stringlength < longline){   printf("the line under minimum length\n");     }     else if (stringlength > longline){         printf("%s", line);     }   return 0; }   int getlinelength(char line[], int maxlinelength){   int i, c;    for(i = 0; i< maxlinelength-1 && ((c = getchar())!= eof) && c != '\n'; i++)     line[i] = c;    if(c == '\n') {       line[i] = c;       i++;   }    line[i] = '\0';   return i; } 

from understand, when parameters declared in function value being passed them, must surely declared somewhere else have value passed in?

in case, function being declared , defined @ same time. pre-ansi c allowed that. considered bad practice today. should add forward declaration

int getlinelength(char line[], int maxlinelength); 

above main in order avoid declaring function implicitly.

when forward declaration missing, first use of function becomes implicit declaration. compiler takes types of expression parameters pass, , assumes function takes corresponding types parameters. assumes function returns int. in case compiler has information necessary figure out correct signature, function defined correctly. however, in more complex cases (say, if maxlinelength declared long long, not int) lead undefined behavior, should include forward declaration of functions.