Advanced exercises C language

Question 1:

What is the printed data?

#include<stdio.h>
int main() {
	unsigned char i = 7;
	int j = 0;
	for (; i > 0; i -= 3) {
		++j;
	}
	printf("%d\n", j);
	return 0;
}

A.2 B. Infinite loop C.173 D.172

Parsing: C

 Question 2:

Which of the following options must set the second bit of the flag to 0 ()

A. flag&=~2;

B.flag|=2;

c.flag^=2;

D.flag>>=2;

Analysis: A

Question 3:

In the case of #pragma(4) and #pragma(8), how much space does each occupy?

struct One {
	double d;
	char c;
	int i;
};
struct Two {
	char c;
	double d;
	int i;
};

A.16,24,16,24;

B.16,20,16,20;

C.16,16,16,24;

D.16,16,24,24;

Parsing: C

 Question 4:

What is the printed data?

#include<stdio.h>
#include<stdio.h>
void main() {
	int a = -3;
	unsigned b = 2;
	long c = a + b;
	printf("%ld\n", c);
}

A.-1 ;

B.4294967295;

C.0x7FFFFFFF;

D.0xFFFFFFFF;

Analysis: A

 Question 5:

What is the value of i?

int f(int x) {
    return ((x > 2) ? x * f(x - 1) : 3);
}
int i = 1;
i = f(f(2));

A.30；

B. Infinite recursion;

C.9;

D.2160; 

Parsing: C

 Question 6:

The running result of fun(21) is ()

int fun(int x) {
	a ^= (1 << 5) - 1;
	return a;
}

A.10 B.5 C.3 D.8

Analysis: A

Topic 7:

Which of the following statements about C/C++ is incorrect:

A. The macro definition does not check the parameter type, which may cause security risks;

B. Macro-defined constants are easier to understand. If macro-defined constants can be used, avoid using const constants;

C. Too many nested definitions of macros will affect the readability of the program;

D. Compared with function calls, macro definitions can improve the running efficiency of the program;

 Analysis: B

Question 8:

Which of the following descriptions about pointers is incorrect ()

A. After using the free function to release the content of a pointer, the value of the pointer variable was set to NULL;

B. The length of any type of pointer in 32-bit systems is 4 bytes;

C. The data type of the pointer declares the data type of the content actually pointed to by the pointer;

D. Wild pointers point to unallocated or released memory space;

Analysis: A