这个每一步过程是啥意思？

#include <stdio.h> 
  #define  M  3
  #define  N  4
  void fun ( int tt[M][N],int pp[N] )
  {
    int i,j,t;    
    for(i=0;i<N;i++)
    {   
        t=tt[0][i];
        for(j=0;j<M;j++)
        { 
            if(tt[j][i]<t)
             t=tt[j][i];    
        }
        pp[i]=t;    
    } 
  } 
  main()
  { 
    int t [ M ][ N ]={{30,55,90,30},
 
                      {19,33, 45,38},
 
                      {20,22, 66,40}};
     int  p [ N ],  i,  j,  k;
     printf ( "The original data is : \n" );
     for( i=0; i<M; i++ )
     {
         for( j=0; j<N; j++ )
 
             printf ( "%6d", t[i][j] );
 
         printf("\n");
     }
     fun ( t, p );
     printf( "\nThe result  is:\n" );
     for ( k = 0; k < N; k++ )
         printf ( " %4d ", p[ k ] );
     printf("\n");
 
  } 

有帮助的话麻烦采纳一下