01
(Multiple Choice) To define a one-dimensional array a with 10 int elements, the following definition statements arecorrect:
A) #define N 10
int a[N];
B) #define n 5
int a [2*n];
C) int a[5+5];
D) int n=10,a[n];
Answer: ABC
Explanation:
For option D: In the C89 standard, the size of an array must be a constant expression, not a variable.
02
(Multiple Choice) The number systems that can be represented in C language source programs are
A) Binary
B) Octal
C) Decimal
D) Hexadecimal
Answer: BCD
Explanation:
For option A: Traditional C language (C89) does not support direct binary representation and requires manual conversion.
For option B: C language supports it, using the 0 prefix:
For option C: Directly writing numbers without a prefix:
For option D: C language supports it, using 0x or 0X prefix:
03
(Multiple Choice) According to the naming rules for user identifiers in C language, the following can appear in identifiers:
A) Uppercase letters
B) Connectors
C) Digits
D) Underscores
Answer: ACD
Explanation: Brief
04
(Multiple Choice) The followingillegal character constants are ( )
A) ‘\x13’
B) ‘\081’
C) ‘\065’
D) “\n”
Answer: BD
Explanation:
For option A: ‘\x13’ is a valid hexadecimal escape sequence;
For option B: ‘\081’ seems to be an octal escape sequence (\ followed by 1-3 octal digits), but the octal digit range is 0-7, and 8 is an illegal character;
For option C: ‘\065’ is a valid octal escape sequence;
For option D: “\n” is a string constant (enclosed in double quotes), not a character constant;
05 (Common Mistake)
(Multiple Choice) The followingvalid character constants are
A) ‘\018’
B) ‘”‘
C) ‘\\’
D) ‘\0xcc’
Answer: BC
Explanation:
For option A: Single quotes ” indicate character constants, not string constants;
For option B: The representation method for escaped characters in double quotes. Note: The representation method for escaped characters in single quotes is ‘\”, and the representation method for escaped question mark is ‘\?’
For option C: The representation method for the backslash;
For option D: ‘\0xcc’ is also illegal because \0xcc is not a valid escape sequence (hexadecimal escape should be \xcc);
06
(Multiple Choice) The following statements arecorrect:
A) C statements must end with a semicolon
B) Compound statements are syntactically considered a single statement
C) Empty statements do not affect program execution regardless of their position
D) Adding a semicolon at the end of an assignment expression constitutes an assignment statement
Answer: ABD
Explanation:
For option C: An empty statement (just a semicolon 😉 may lead to logical errors in certain positions.
07 (Common Mistake)
(Multiple Choice) The followingvalid assignment statements are
A) n=(i=2,++i);
B) j==1;
C) ++(i+1);
D) x=j>0;
Answer: AD
Explanation:
For option B: This is a relational expression (checking if j equals 1), not an assignment statement;
For option C: The increment operator ++ must have a modifiable lvalue (like a variable) as its operand; i+1 is a temporary computed result, not a modifiable lvalue;
08
(Multiple Choice) The following cancorrectly define a two-dimensional array:
A) int a[2][2] = {{1}, {2}};
B) int a[ ][2] = {1, 2, 3, 4};
C) int a[2][2] = {{1}, {2},{3}};
D) int a[2][ ] = {{1, 2}, {3, 4}};
Answer: AB
Explanation:
For option C: Defined a 2×2 array but provided 3 rows of initialization data ({1}, {2}, {3});
For option D: When defining a two-dimensional array, note that the number of columns cannot be omitted; in C language, the number of rows can be omitted, but the number of columns must not be omitted;
09
(Multiple Choice) If there is a definition: int a[8]; then the following expressions that can represent the address of array element a[1] are
A) &a[0]+1
B) &a[1]
C) &a[0]++
D) a+1
Answer: ABD
Explanation: Brief
10
(Multiple Choice) Given the definition: int i,a[10],*p; , the followingillegal assignment statements are
A) p=100;
B) p=a[5]
C) p=&a[2]+2
D) p=a+2;
Answer: AB
Explanation: Brief