c - Why am I getting a value of 0 for my min and max? -

#include <stdio.h> #include <stdlib.h> #include <time.h> /* initialize random generator */ #define buff_size 10 #define 5 five #define ten 10 #define 0 0 #define 1 one float min=0; float max=0; float average=0; float input_buffer[buff_size+2] = {0}; float output_buffer[five] = {0}; float local_buffer[ten]; int no_of_data_pts=0; int function_id=0;  // function generating data size, function id , // data, , putting of input_buffer void generate_data() {     /* initialize random seed: */     srand ( time(null) );     /* generate random number: */     input_buffer[0] = floor(1 + 10*(float)rand()/rand_max);     input_buffer[1] = floor(1 + 4*(float)rand()/rand_max);     int i;     (i=0; < (int)input_buffer[0]; i++ ){         input_buffer[i+2]=(float)rand()/rand_max;     } }  // function copying content of input_buffer // local buffer (called here my_buffer) void reading() {     no_of_data_pts= (int)input_buffer[0];     function_id= (int)input_buffer[1];     int i;     (i=0; < no_of_data_pts; i++ ){         local_buffer[i]=input_buffer[2+i];     } }  // function processing content of local buffer; // reads function_id , number of data points my_buffer // , saves results my_buffer void processing() {     float num=0;     int i;     float sum = 0;     float min=0;      (i=0; i<no_of_data_pts; i++){        num = local_buffer[i+1];        if (num < min) {            min=num;        }     }      (i=0;i<no_of_data_pts;i++){        num = local_buffer[i+1];        if (num < max) {            max=num;        }     }      (i=0;i<no_of_data_pts;i++) {        sum = sum + local_buffer[i];     }     average = sum/no_of_data_pts; }  // function copying content of my_buffer // output_buffer (according patter explained earlier) void writing() {     switch (function_id){          case 1:             output_buffer[0]= min;             printf ("minimum value is: %f ",output_buffer[0]);             break;         case 2:             output_buffer[0]= max;             printf ("maximum value is: %f ",output_buffer[0]);             break;         case 3:             output_buffer[0]= average;             printf ("average value is: %f ",output_buffer[0]);             break;         case 4:             output_buffer[0]= min;             output_buffer[1]= max;             output_buffer[2]= average;             printf ("minimum, maximum , average value is: %f,%f,%f ",output_buffer[0],output_buffer[1],output_buffer[2]);             break;     }   }  int main () {     setvbuf(stdout, null, _ionbf, 0);      setvbuf(stderr, null, _ionbf, 0);      generate_data();     reading();     processing();     writing();     return 0; } 

so c assignment.

so when run code, it's supposed generate random numbers 0 1 , calculate min, max , average.

the reading of data input buffer involves:

• reading number first element of input buffer, if non-zero number (and should be), program performs 2 following operations, number represent number of data points read (no_of_data_points)
• reading id of processing function (function_id)
• reading data points id of data processing function , points read local buffer

the processing of data involves:

• based on read id of processing function specific calculations performed, 4 different processing can take place:
• if id 1: minimum of data points determined
• if id 2: maximum of data points determined
• if id 3: average of data points determined
• if id 4: minimum, maximum , average of data points determined results should placed local buffer.

the writing of data output buffer involves:

• writing number indicating how many data points written output buffer (it includes id of processing function, , obtained results)

• writing number, called id of processing function, indicating operation performed on data (range 1 4)

• writing result, , depends functions was:

§ if id 1: value of minimum written

§ if id 2: value of maximum written

§ if id 3: value of average written

§ if id 4: values of minimum, maximum , average written

i print results @ end of program.

the code runs fine. there no errors reason, cannot figure out why values of min , max 0! value average fine max , min values 0 reason , that's not right.

for starters, this

   if (num < max) {        max = num;    } 

shall

   if (num > max) {        max = num;    } 

at least.

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also using above approach initialising min , max 0 might not work kind of input.

to sure detect possiblities of input initialise

min = flt_max; 

and

max = -flt_max; 

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if smallest/largest possible values unknown reason, change way how min , max being detected:

void processing() {   float num=0;   int i;   float sum = 0;    min = local_buffer[1];   (i = 1; < no_of_data_pts; i++){     num = local_buffer[i + 1];     if (num < min) {        min = num;     }   }    max = local_buffer[1];   (i = 1; < no_of_data_pts; i++){     num = local_buffer[i + 1];     if (num > max) {        max = num;     }   }    ... 

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also^2 code defines min twice:

1. globally
2. local processing(), shadowing 1.

remove 2^nd definition.

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the code misses protoype floor(). that's why compiler assume return int. might invoke undefined behaviour.

to fix add

#include <math.h> 

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also^3 when reading out local_buffer in processing() code use wrong indexing. index starts @ 0 not @ 1. reading out last value had not been set generator. that's 0 min comes from.

correcting make above snippet processing() like:

void processing() {   float num=0;   int i;   float sum = 0;    min = local_buffer[0];   (i = 1; < no_of_data_pts; i++){     num = local_buffer[i];     if (num < min) {        min = num;     }   }    max = local_buffer[0];   (i = 1; < no_of_data_pts; i++){     num = local_buffer[i];     if (num > max) {        max = num;     }   }    ... 

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final notes:

1. listen compiler, take warnings serious.
2. you might take consideration learning how use debugger, able figure such issues on own next time.