College C language final exam · multiple choice questions · summary notes of mistakes and difficulties

This is my wrong question , Then sum up the wrong knowledge points , Each set of questions has a number segment

First set of questions

1、% Binary operator , Left binding , Both left and right are integers , Cannot be double

2、 Array 【0】 The first and 【4】 The fifth one ,

3、 character 0 by NULL

4、 Precautions when defining structure variables typedef,struct

5、0 The beginning octal cannot have 8、0x Start with hex 、 Hexadecimal has abcdef

6、e Said to 10 The idempotent of the base , Must be an integer ,e There should be numbers at the front and back

7、 identifier ： Letter 、 Underline 、 Digital composition ,,, Keywords cannot be , Can 't start with a number

8、pow( base number , Power number ),abs() Integer absolute value ,fabs() Floating point absolute value ,exp(e Of n Power )

9、getchar（） Read a number one by one

10、 The logical operator can be any legal expression

11、x It is greater than 1 The odd number x%2 == 0 error

12、while(a–); Last a==-1. The grass is wrong but while I haven't received

13、void (*pf)() Pointer function ,void *pf() The return value is a pointer variable

14、char *s; s=“BOOK!”

15、 character string ’\0’ Not counting the character length

16、\,\n The conversion character in the string , Count one character each

17、 Automatic variable auto, Not automatically assigned determine Initial value of .

18、 Static variables satic, The initial value will not be assigned every time .

19、 Angle sign of array variable

20、 Pass a value to the address of a pointer variable , The original value does not change .

21、 Calculation in macro definition #define f（x） xx quote f(a+1) = a+1a+1a+1 = 3a+1;f((a+1))=44*4=64

The second set of questions

1、 Formal and actual parameters of structure variables , Value transmission and address transmission are different .

6、 Octal number 0 Start with and cannot contain numbers 8

7、 Equal sign = Right knot and sex , You cannot assign a number to an expression .

8、a=(b=4)+(c=6),, have to a = 10;+ first =

9、 The input data format must be the same as scanf() The format control strings in the match exactly scanf("%d;%d",&a,&b); Input required 3;5

10、#define The defined formula directly calculates #define M N+1 #define N 5 #define f(x) (xM) == xN+1

11、feof(fp) If you read to the end of the file ,eof Function value is 0 value , Otherwise 0

12、 Prime numbers can only be 1 Or the number divided by itself

The third set of questions

1、 Symbolic Constant refers to the constant represented by a symbolic name through macro definition in the program #define

2、if When the condition is logic and expression ,&& If the first is false, the second expression will not be judged （ Short circuit principle ）

3、switch The statement did not break It runs all the time

4、 Macro definitions make simple substitutions

5、10^5=15 Exclusive or operation , Different at the same time 1

6、 Software design is divided into high cohesion and low coupling 、 The module size and scale are appropriate 、 The dependencies of the modules are appropriate

7、 Constants do not belong to identifiers

Fourth set of questions

1、 Real constant （ Floating point numbers ） There is only one decimal system

2、&& and || Short circuit of logic expression , After the previous expression evaluates , The latter expression may not be calculated

3、#include The command line can appear in the middle of the program file

4、++P->a The effect is that members a increase 1

5、switch Statement has no semicolon

6、#define The statement also has no semicolon

7、 Pointer to string ,sizeof（b） = 4, Four bytes

8、 Pointer variable name -> Member name ,（* Pointer variable name ）. Member name ,

The fifth set of questions

1、 Row coordinates cannot be omitted when defining a two-dimensional array

2、 Character arrays cannot be assigned directly mark=“abc”, It seems that the pointer can

3、 When the pointer points to the first address of an array , You can use p[3] Use

4、*p++ Same operation priority , Right to left , Present address +1 Then take the content

5、 The comma operator , Take the last value （a+b,b+3）

6、 Do not use the address character when entering the array name &

7、 Short circuit principle ,a=b=c=d=m=n=2;(m=a>b)&&(n=c>d)

8、 To define an array int a[2][]={ {1,2},{3,4}} error int d[3][2]={ {1,2,1},{1,2,3},{1,2,3}} The error exceeds the limit

9、 The second of the array definitions [] Cannot omit , If omitted, you will not know how many columns there are , Infinite columns overflow

10、 From the main Start to... Of this procedure main End of the function

Sixth set of questions

1、strcmp(s,t) Compare s>t Return greater than 0 Number of numbers

2、int a=5,b=4,c=3; d =（a>b>c） The result is 0,,, Because first run a>b The result is 1, then 1>c For false

3、for(i=9;i>=0;i–) a[i] = 10 - i; Be careful a[i] Also from the 9 At the beginning

4、a[10]= {10,9,8,7,6,5,4,3}; sum(&a[2]); a[0]=a[1]+a[2]; The result is a[2] = a[3]+a[4]

5、int x=1,y=1; (!x||y–) The value of is 1, He is or

The eighth set of questions

1、 It can be expressed correctly a and b A logical expression that is both positive and negative a*b>0

2、printf("%s,%8s,%8.3s",“china”,“china”,“china”) china,000china,00000chi

3、 Functions cannot be nested

4、strcmp()
（1）strcmp Is to compare the size of two strings , Returns... When two strings are the same 0, Returns a positive value when the first string is greater than the second string , Otherwise, a negative value is returned .
（2） The algorithm for comparing two strings is ： Compare the corresponding characters in two strings one by one , The character size is in accordance with ASCII Code value determination , Compare from left to right , If you encounter different characters , The size relationship of the first pair of different characters determines the size relationship of the two strings , If no different characters are encountered and a string ends first , So this string is smaller , Otherwise, the two strings are equal .

5、 C Language parameter list a[ ] What does that mean? , How to use it? ？
Represents a pointer , The array name is actually a pointer to the first element of the array , When actually calling, just pass the array name as an argument to the formal parameter of the function

6、 If it's an expression, it must have a number —— Assignment expression ： The expression value is the leftmost value ,a=b=5, The expression is 5, Constant cannot be assigned ,printf("%d",a=5+9) Output 14

7、&& and || Short circuit phenomenon of , priority ！ > && > ||

8、018 The value of is illegal , Octal is not 8 Of

9、% Both sides of the symbol are required to be integers , It's not a whole number

10、%ld yes long int Format output

additional :

1、do-while Behind a ; A semicolon

2、！= Number is higher than = while(c=getchar()!=’/n’) and while((c=getchar())!=’/n’) difference , Input ab I will be the first c=1, The second is ab

3、*p++ and （p）++ The difference between , The first is p Address to add 1 Then the value is taken , The second is after the value , It's worth adding 1,++ Has a higher priority than

4、 Array name ： Represents the address of the first element , Array name cannot be added by itself , He is the address constant name , if a[10] As long as there is a++,a=a+2 That is wrong

5、a+1=&a[1]

6、 int a[]={1,2} legal ,int a[][4]={2,4,5} legal int a[4][]={2,3,4} illegal , The second one in two dimensions is the column

Then there are a few easy and slightly difficult questions ：