Midterm CSE 131 Spring 2015

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1 Login Name _ Signature Name _ Student ID Midterm CSE 131 Spring 2015 Page 1 Page 2 Page 3 Page 4 Page 5 (28 points) (24 points) (28 points) (28 points) (36 points) Subtotal (144 points = 100%) Page 6 Extra Credit (8 points) Total This exam is to be taken by yourself with closed books, closed notes, no electronic devices. You are allowed one side of an 8.5"x11" sheet of paper handwritten by you. 0

2 1. Given the following CUP grammar snippet (assuming all other Lexing and terminals are correct): Expr ::= Expr T_PLUS {: System.out.println("A"); : Des {: System.out.println("B"); : Des {: System.out.println("C"); : ; Des ::= T_STAR {: System.out.println("D"); : Des {: System.out.println("E"); : T_AMPERSAND {: System.out.println("F"); : Des {: System.out.println("G"); : T_PLUSPLUS {: System.out.println("H"); : Des {: System.out.println("I"); : Des2 ; Des2 ::= Des2 {: System.out.println("J"); : T_PLUSPLUS {: System.out.println("K"); : Des2 {: System.out.println("L"); : T_LBRACKET Expr T_RBRACKET {: System.out.println("M"); : Des2 {: System.out.println("N"); : T_DOT T_ID {: System.out.println("O"); : Des3 ; Des3 ::= T_ID {: System.out.println("P"); : T_INT_LITERAL {: System.out.println("Q"); : ; What is the output when parsing the follow expression (you should have 21 lines/letters in your output): [21pts] Output z[0].y x.y[0] In the above grammar, does the addition (+) operator have left-to-right or right-to-left associativity? _ [2pts] If variables x and z were defined as below, what value should the expression above result in at runtime? [5pts] structdef MS1 { int * y; ; structdef MS2 { int y; ; int a = 9; int b; int * c = &a; int * d = &b; MS1 x; MS2 z[1]; function : void main() { x.y = (&c)[0]; z[*d].y = (*c)++; cout << z[0].y x.y[0]; ----> 1

3 2. Show the memory layout of the following C struct definition taking into consideration the SPARC data type memory alignment restrictions discussed in class. Fill bytes in memory with the appropriate struct member/field name. For example, if member/field name p takes 4 bytes, you will have 4 p's in the appropriate memory locations. If the member/field is an array, use the name followed by the index number. For example, some number of p[0], p[1], p[2], etc. If the member/field is a struct, use the member name followed by its member names (e.g. p.a, p.b, etc.). If the member/field is an array of structs, include both the index and member name (e.g. p[0].a). Place an X in any bytes of padding. Structs/unions are padded so the total size is evenly divisible by the strictest alignment requirement of its members. [14pts figure; 10pts questions] struct dumb { int a; char b[5]; ; struct by { short c; int d; char e; struct dumb f; double * g[2]; char h[4]; double i; short j; ; struct by lightning; low memory lightning: high memory What is the sizeof( lightning )? _ What is the offsetof( struct by, h[1] )? _ If struct by had been defined as union by instead, what would be sizeof( union by )? _ If you rearrange the order of the struct members in struct by to minimize padding, what would be the size of this modified struct by? _ How many bytes are saved by rearranging the struct by members to minimize padding? _ 2

4 3. Given the following pseudocode, determine the program output based on the specified scoping rule: [28pts] int x = 0; int y = 0; void sum_xy( int a, int b ) x = x + a; y = y + b; -- global var declaration -- global var declaration void rock() int y = 2; -- local var declaration sum_xy( 1, 1 ); cout << x << endl; cout << y << endl; void paper() int x = 9; -- local var declaration sum_xy( 4, 8 ); rock(); cout << x << endl; cout << y << endl; void scissors () int x = 2; -- local var declaration int y = 9; -- local var declaration sum_xy( 3, 1 ); paper(); cout << x << endl; cout << y << endl; sum_xy( 4, 5 ); rock(); paper(); scissors(); cout << x << endl; cout << y << endl; What does the program output if the language uses static scoping? What does the program output if the language uses dynamic scoping? 3

5 4. Given the C array declaration on a SPARC architecture C short a[2][7]; What is the sizeof( a )? Mark with an A all the memory location(s) where we would find the array element a[1][6]: [2pts] [4pts] a: lower memory (Each box represents a byte in memory) higher memory Given the following Reduced-C code structdef S1 { bool b; int i; float f; ; structdef S2 { bool b; int i; float f; ; structdef S3 { bool b; int i; float f; ; S1 a; S1 b; S2 c; S2 d; S3 e; S3 f; identify each of the following statements as either: [18pts] (A) No Error (B) Compile-Time Error a = b; c = d; a = (S1) f; a = c; c = e; a = * (S1*) &f; a = d; c = f; (S2) b = d; a = e; e = f; * (S2*) &b = e; a = f; a.i == f.i; * (S1*) &e = b = a; d.f = f.i; b.i = a.f; a.i = c.i = e.i; Using the Right-Left Rule, give the C variable declaration for a variable named sungod that is a pointer to a pointer to a pointer to a function that takes an int and a double as two parameters and returns a pointer to an array of 4 elements where each element is a double. [4pts] 4

6 5. Given the following C code, indicate which of the 5 main areas of the C Runtime Environment each expression is located in: [18pts] int A; static int B; int * C ( int D, int E ) { static float F = 3.14; int G = D + E; A _ I _ B _ *I _ C _ J _ D _ K _ return &G; E _ *K _ int main ( int argc, char *argv[] ) { F _ L _ int * H; H = (int *) calloc(1, sizeof(int)); G _ *L _ int * I = C( argc, *H ); static int J = 5; H _ **L _ int * K = &J; int ** L = &I; *H _ argc _ **L = 17; < determine runtime areas at this point in time free(h); H = NULL; return 0; What programming error exists in the code above? What occurs when an object lives longer than its binding? [2pts] [2pts] What occurs when a binding lives longer than its object? [2pts] Given the following C code, indicate the output for each statement, or -1 if the statement is an error: [4pts] #include <stdio.h> void main() { int arr[5] = {1, 2, 3, 4, 5; printf("%d\n", arr[3]); printf("%d\n", arr[arr[arr[1]]]); printf("%d\n", 4[arr]); printf("%d\n", arr[arr[1]+0[arr]]); Identify the following C constructs as either: (A) Pure Declaration (B) Definition [8pts] _ int ** foo ( int x, float y); _ struct baz * foo( int x ); _ void foo() { _ float * y; _ extern int x; _ struct fubar { int x; s1; _ extern int a[50][50]; _ extern int ******** p; 5

7 Extra Credit What gets printed when the following C program is executed? [8pts] #include <stdio.h> int main() { char a[] = "ULTRON"; char *p = a; printf( "%c\n", a[5] = (*p++ = 5[a]) + 5 ); printf( "%c\n", a[2] = (*p++ = 4[a]) - 6 ); printf( "%c\n", p[3] = p[1] + 4 ); printf( "%c\n", ++*++p - 1 ); printf( "%c\n", *p ); printf( "%c\n", (*p = p[-2]) + 1 ); printf( "%s\n", a ); _ return 0; A portion of the C Operator Precedence Table Operator Associativity ++ postfix increment L to R -- postfix decrement [] array element () function call * indirection R to L ++ prefix increment -- prefix decrement & address-of sizeof size of type/object (type) type cast * multiplication L to R / division % modulus + addition L to R - subtraction.. = assignment R to L Hexadecimal - Character 00 NUL 01 SOH 02 STX 03 ETX 04 EOT 05 ENQ 06 ACK 07 BEL 08 BS 09 HT 0A NL 0B VT 0C NP 0D CR 0E SO 0F SI 10 DLE 11 DC1 12 DC2 13 DC3 14 DC4 15 NAK 16 SYN 17 ETB 18 CAN 19 EM 1A SUB 1B ESC 1C FS 1D GS 1E RS 1F US 20 SP 21! 22 " 23 # 24 $ 25 % 26 & ( 29 ) 2A * 2B + 2C, 2D - 2E. 2F / A : 3B ; 3C < 3D = 3E > 3F? 41 A 42 B 43 C 44 D 45 E 46 F 47 G 48 H 49 I 4A J 4B K 4C L 4D M 4E N 4F O 50 P 51 Q 52 R 53 S 54 T 55 U 56 V 57 W 58 X 59 Y 5A Z 5B [ 5C \ 5D ] 5E ^ 5F _ a 62 b 63 c 64 d 65 e 66 f 67 g 68 h 69 i 6A j 6B k 6C l 6D m 6E n 6F o 70 p 71 q 72 r 73 s 74 t 75 u 76 v 77 w 78 x 79 y 7A z 7B { 7C 7D 7E ~ 7F DEL 6

8 Scratch Paper 7

Memory is implemented as an array of electronic switches

Memory Structure Memory is implemented as an array of electronic switches Each switch can be in one of two states 0 or 1, on or off, true or false, purple or gold, sitting or standing BInary digits (bits)