Programme langage C

• tes tests du type

  if (99<prix<500) {

  ne font pas ce que tu penses. En C il faudrait écrire

  if ( (99<prix) && (prix<500) ) {

  pour avoir l'effet recherché
• à la ligne

  if(500<prix<1000);{

  , en plus du problème similaire à celui ci-dessus, tu as mis un

  ;

  après la parenthèse, comme si tu voulais terminer ton instruction (et que tu dois bien sûr retirer)
• tes tests seront toujours faux, car tu compares la variable

  prix

  à ces bornes, alors que

  prix

  vaut

  0

  à ce stade, car c'est dans

  x

  que tu fais ton addition
• probablement, en fin de programme, tu voudras afficher

  prix

  , qui est la variable contenant le résultat de ton calcul de remise, non ?

$ gcc -Wall 36879476.c
36879476.c: In function ‘main’:
36879476.c:6:3: warning: implicit declaration of function ‘printf’ [-Wimplicit-function-declaration]
   printf ("saisir prix\n");
   ^~~~~~
36879476.c:6:3: warning: incompatible implicit declaration of built-in function ‘printf’
36879476.c:6:3: note: include ‘<stdio.h>’ or provide a declaration of ‘printf’
36879476.c:1:1:
+#include <stdio.h>
 int main (void)
36879476.c:6:3:
   printf ("saisir prix\n");
   ^~~~~~
36879476.c:7:3: warning: implicit declaration of function ‘scanf’ [-Wimplicit-function-declaration]
   scanf("%f",&prix);
   ^~~~~
36879476.c:7:3: warning: incompatible implicit declaration of built-in function ‘scanf’
36879476.c:7:3: note: include ‘<stdio.h>’ or provide a declaration of ‘scanf’
36879476.c:10:13: warning: comparison of constant ‘500’ with boolean expression is always true [-Wbool-compare]
  if (99<prix<500) {
             ^
36879476.c:10:8: warning: comparisons like ‘X<=Y<=Z’ do not have their mathematical meaning [-Wparentheses]
  if (99<prix<500) {
      ~~^~~~~
36879476.c:13:13: warning: comparison of constant ‘1000’ with boolean expression is always true [-Wbool-compare]
  if(500<prix<1000);{
             ^
36879476.c:13:8: warning: comparisons like ‘X<=Y<=Z’ do not have their mathematical meaning [-Wparentheses]
  if(500<prix<1000);{
     ~~~^~~~~
36879476.c:13:2: warning: this ‘if’ clause does not guard... [-Wmisleading-indentation]
  if(500<prix<1000);{
  ^~
36879476.c:13:20: note: ...this statement, but the latter is misleadingly indented as if it were guarded by the ‘if’
  if(500<prix<1000);{
                    ^
36879476.c:19:2: warning: incompatible implicit declaration of built-in function ‘printf’
  printf("total : %f\n",x);
  ^~~~~~
36879476.c:19:2: note: include ‘<stdio.h>’ or provide a declaration of ‘printf’

#include <stdio.h>

int main ()
{
    float prix;
    float x=0;
    do {
        printf ("saisir prix\n");
        scanf("%f",&prix);
        x = x+prix;
    } while( prix != 0);
    if ((99<x)&&(x<500)){
        prix=x*0.9;
    }
    if((500<x)&&(x<1000)){
        prix=x*0.8;
    }
    else{
        prix=x*0.7;
    }
    printf("total : %f\n",prix);   
    
}