FWRITE function is not writing in binary format in C language

Question

I am not able to write data in binary in a file using the C language. Even using 'Wb' the output of the file are characters. How can I proceed? Here’s part of my code:

void cadastrar(void)
{
     if((fp=fopen("Jogos.dat", "wb"))==NULL)
     {
        printf("\nO arquivo nao pode ser aberto!\n");
        getch();
        exit(1);
     }
     fseek(fp,0L, SEEK_END);

do { printf("\n Digite o Nome do Jogo ('FIM' para sair): "); gets(reg[quantidade_cadastro].nome_jogo); if ((strcmp(reg[quantidade_cadastro].nome_jogo,"fim")!=0)&&(strcmp(reg[quantidade_cadastro].nome_jogo,"FIM")!=0)) { printf("\n Ano de Lancamento: "); scanf("%d",&reg[quantidade_cadastro].ano_lancamento); fflush(stdin); printf("\n Genero: "); gets(reg[quantidade_cadastro].genero); printf("\n Plataforma: "); gets(reg[quantidade_cadastro].plataforma); reg[0].status='1'; if(fwrite(&reg, sizeof(struct registro), 1, fp) != 1) { printf("\nErro de Gravacao :/"); getch(); } else { quantidade_cadastro++; printf("\n Jogo Gravado no Arquivo!\n\n"); } } }while((strcmp(reg[quantidade_cadastro].nome_jogo,"fim")!=0)&&(strcmp(reg[quantidade_cadastro].nome_jogo,"FIM")!=0)); fclose(fp);}

Answer 1

Your file has characters for the following reason.

As his struct consists of 4 fields char and a field int, the normal is that the data can be read.

The method fwrite writes directly the values of your struct file, without converting values such as the printf.

The values used are those in the table ascii. Assuming you have the following string "ABCD", the values would be written as: 65,66,67,68. And when the text editor would read these values it would display ABCD.

Case a int be written in the file, the size of the int in 64bits vale 4, and the value to be written will be 65. The value written in the file will be 65,0,0,0 or To to the text editor. If the written value is 16961, shall write AB.

If you use the command string (present in the gcc/ bin) it will be possible to see the names of the methods, the strings and the libraries used by your system, because of the interpretation of the table ascii when you read the file.

If you want a file with unreadable values (no characters A-Za-z-0-9), you must store values that escape as much as possible from literary and numerical characters.

Answer 2

The contents of type objects struct registro is basically just text. No wonder the contents of the file are characters.

Check the part of ano_lancamento in the file "Games.dat".

How would you like the next entry to be presented "in binary"?

strcpy(reg[0].nome_jogo, "jogo um");
reg[0].ano_lancamento = 2014;
strcpy(reg[0].genero, "sorte");
strcpy(reg[0].plataforma, "papel e lápis");

The difference between a text or binary file is basically in the handling of "\n". A binary file does not handle this character, a text file can convert to "\r\n". For more details read the sections 7,21,2 and 7.21.3 of Standard C11 (in English).