【Day06_0423】C Language multiple choice questions

1. Decimal variables i The value of is 100, So octal variables i The value of is :（C）

A 146
B 148
C 144
D 142

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2. The output after executing the following statement is （）

int I = 1;
if (I <= 0)
{
    
	printf("****\n");
}
else
{
    
	printf("%%%%\n");
}

A %%
B ****
C There is a grammatical error , Cannot execute correctly
D %%%%
His answer ： D ( error )
right key ： A

analysis ：
Every two % For a group , The first represents control , because % No. followed by a specific character can be used for format control , and % Followed by the second % No special meaning , So the second in each group % Will be output .
eg.%Q, Will directly output characters Q

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3. For the following C One of the things that language statements describe correctly is （C）

char (*p)[16]

A p It's a length of 16 Character pointer array of
B p Is included 16 Character string
C p Yes, the pointing length is 16 Pointer to the character array of
D p It's a length of 16 Array of characters

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4. Array a The definition statement of is “float a[3][4];”, The following （D ） Is an incorrect reference method to an array element .

A a[i] [j]
B *(a[i]+j)
C *(*(a+i)+j)
D *(a+i*4+j)

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5. The output of the following program is （d）

#include < iostream.h>
#define SQR(A) A*A
void main() {
    
	int x = 6, y = 3, z = 2;
	x /= SQR(y + z) / SQR(y + z);
	cout < < x < < endl;
}

A 5
B 6
C 1
D 0

analysis ：
Right side of the formula ：3+2*3+2/3+2*3+2=3+6+0+6+2=17
6/17=0

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6. When n=5 when , The return value of the following function is ：（）

int foo(int n) {
    
	if (n < 2) {
    
		return n;
	}
	else
		return 2 * foo(n - 1) + foo(n - 2);
}

A 5
B 11
C 29
D 10

analysis ：
Calculate recursion problem , From the bottom up
f5=2f4+f3
f4=2f3+f2
f3=2f2+f1
f2=2f1+f0;
f1=1;
f0=0;
Then push up , obtain f5 Result

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7. The following for C Linguistic ” The pointer “ What's wrong with the description is ：（D）

A 32 The length of any type of pointer in a bit system is 4 Bytes
B The data type of the pointer declares the data type that the pointer actually points to the content
C A wild pointer is a pointer to an unallocated or freed memory address
D When using free After releasing a pointer content , The value of the pointer variable is set to NULL

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8. Array is defined as ”int a[4][5];”, quote ”*(a+1)+2″ Express （）( From 0 OK, let's start )

A a[1][0]+2
B a Array number 1 Xing di 2 The address of the column element
C a[0][1]+2
D a Array number 1 Xing di 2 Value of column element

analysis ：
No dereference does not mean value , Address

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9. There's a structure like this ： Excuse me at 64 Bit compiler sizeof(struct A) What's the calculated size ？（）

struct A {
    
	long a1;
	short a2;
	int a3;
	int* a4;
};

A 24
B 28
C 16
D 18
His answer ： A ( correct )
right key ： A

analysis ：
64 Bit compiler , therefore int* Occupy 8 Bytes , The default alignment number is 8 Calculation

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10. The result of the operation is ？（D）

#include <iostream>
using namespace std;
int f(int n) {
    
	if (n == 1)
		return 1;
	else
		return (f(n - 1) + n * n * n);
}
int main() {
    
	int s = f(3);
	cout << s << endl;
	return 0;
}

A 8
B 9
C 27
D 36

analysis ：
Calculation method of recursive problem , Calculate from the bottom to the top
f3=f2+333
f2=f1+222
f1=1