// one-line comment

/**
 * multi-line comment
 * can be /* nested */
 * ignore everything after //
 * like // */
 * like // /*
 * like // *//*
 * like // /*_*/
 */ // This is the end of this multi-line commet!

// int read()
// write(int x)
// are provided functions to support input and output

int echo(int e)
{
    write(e);
    return read();
}

struct A {
    int a;
    int b;
};

int main()
{
    /* Local definitions, like follows */

    int foo;
    int bar = 3;
    int vec[2];
    char hello[5];
    struct A a;

    /* character array */
    hello[0] = 'h';
    hello[1] = 'e';
    hello[2] = 'l';
    hello[3] = 'k' + 1;    //char and calculate with int
    hello[4] = 'o';

    /* Statements, like follows */

    if (/* Expression */) {
        /* Statements */
    }
    else if (/* Expression */) {
        /* Statements */
    }
    else {
        /* Statements */
    }

    while (/* Expression */) {
        /* Statements */
    }

    // the three parts of for-loop cannot be omitted currently
    for (foo = 0; foo < 5; foo = foo + 1) {
        writec(hello[foo]);
    }

    /* Expressions */

    foo = bar;  // Assignment
    foo + 1;    // Binary operation: +, -, *, /
    foo < bar;  // Comparing operation: <, <=, >, >=, ==, !=
    !foo;       // Unary operation: -, !
    a.a         // field access
    (foo);
    foo = echo(vec[0]);  // Function call, array access

    return 0;
}