Getting unnecessary value while concatenating strings

I am getting problem while concatenating strings.I think this is the stupid question,but i didn't get answer.Thats why i am posting here.Please Help me.

The source code is

unsigned char arr_25[] = "{\"category\":\"",
    arr_10[]="FMCG",
    arr_26[]="\"amount\":",
    arr_11[]="\",",
    arr_12[]="1000",
    arr_13[]="}";

float amount=1500,totamount=2500;

for(i=0;i<=count;i++)
{
    if(i>0)
       strcat(buff,",");

    strcat(buff,arr_25);
    strcat(buff,arr_10);//I am getting unnecessary value while printing this arr_10
    strcat(buff,arr_11);
    strcat(buff,arr_26);

    memset(arr_12,0,sizeof(arr_12));

    sprintf(arr_12,"%.2f",amount);
    printf("\n the amount is %s \n",arr_12);

    strcat(buff,arr_12);
    strcat(buff,arr_13);
}

After 开发者_JAVA技巧printing the buff value i am getting

{"category":"FMCG","amount":1500.00},{"category":"FMCG00"amount":1500.00},{"category":"FMCG00"amount":1500.00},{"category":"FMCG00"amount":1500.00} 

I am getting: "FMCG,FMCG00,FMCG00..."

Why does this occur? As i hard coded arr-10 value to FMCG..?

Thanks in Advance....

I don't know if it's the direct reason, but you are certainly overrunning arr_12. You've defined it with size 5 and then you write "1500.00" into it.

you're probably overrunning some variables (arr_12?). Change sprintf with snprintf and you shouldn't have problems.