中软面试题(3)

（3）const int *a; （4）int * const a; （5）int const * a const;

5. Which of the following statements describe the use of the keyword static?

（1）Within the body of a function: A static variable maintains its value between function revocations （2）Within a module: A static variable is accessible by all functions within that module （3）Within a module: A static function can only be called by other functions within that module

6. Embedded systems always require the user to manipulate bits in registers or variables. Given an integer variable a, write two code fragments. The first should set bit 5 of a. The second shnuld clear bit 5 of a. In both cases, the remaining bits should be unmodified.

7. What does the following function return? char foo(void) {

unsigned int a = 6; iht b = -20; char c;

(a+b > 6) ? (c=1): (c=0); return c; }

8. What will be the output of the following C code? main() {

int k, num= 30;

k =(num > 5 ? (num <=10 ? 100:200): 500); printf(“%d”, k); }

9. What will the following C code do? int *ptr;

ptr =(int *)Ox67a9; *ptr = Oxaa55;

10. What will be the output of the follow C code? #define product(x) (x*x) main() {

int i = 3, j, k; j = product(i++); k = product(++i); printf(“%d %d”,j,k);

}

11. Simplify the following Boolean expression !((i ==12) || (j > 15))

12. How many flip-flop circuits are needed to divide by 16?

13. Provides 3 properties that make an OS, a RTOS?

14. What is pre-emption?

15. Assume the BC register value is 8538H, and the DE register value is 62 A5H.Find the value of register BC after the following assembly operations: MOV A,C SUB E MOV C,A MOV A,B SBB D MOV B,A

16. In the Assembly code shown below LOOP: MVI C,78H DCR C JNZ LOOP HLT

How many times is the DCR C Operation executed?

17. Describe the most efficient way (in term of execution time and code size) to divide a number by 4 in assembly language

18. what value is stored in m in the following assembly language code fragment if n=7? LDAA #n

LABEL1: CMPA #5 BHI L3 BEQ L2 DECA BRA L1 LABEL2: CLRA LABEL3: STAA #m

19. What is the state of a process if a resource is not available? #define a 365*24*60*60

20. Using the #define statement, how would you declare a manifest constant that returns the number of

seconds in a year? Disregard leap years in your answer.

21. Interrupts are an important part of embedded systems. Consequently, many compiler vendors offer an extension to standard C to support interrupts. Typically, the keyword is __interrupt. The following routine (ISR). Point out problems in the code.

__interrupt double compute_area (double radius) {

double area = PI * radius * radius; printf(“nArea = %f”, area); return area; }

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