Problem 4. This problem is about two-dimensional arrays (See Section 3.8.3 in the text). The declaration int A[100] [200] declares an array of 100 rows of 200 columns each. An array reference A[i][j] refers to the element in the ith row, jth column. Now, memory is actually linear, so there is a question as to how to compute the address of element A[i][j] The C specification guarantees that such arrays are laid out in row-major order, which means that the elements of row 0 (i.e., all the columns of row 0) come first, followed by the elements of row 1, etc. (Remember: "[Row][Column]") (See Figure 3.16 in the text, also slides 20, 22 and 24 from the lecture "Implementing Data Structures" on Friday 15 September.) a. For the array A declared above (100 rows of 200 columns each), with starting address 200000, what is the address of element A[47] [101]? b. Assume a global array declared as int *ptrs [10] [20]. The address of ptrs is in %rbx. Assume the value of int variables r and c are in registers %rdi and %rsi, respectively, and the last statement of a function that returns a pointer to an int is return ptrs [r] [c]; Write assembly code to put the return value in %rax c. Suppose a two-dimensional array is declared: char foo[M] {N]; where M and N are constants defined elsewhere. If you know that foo[r] [c] (for some values of r and c) is the same as *(foo+120), is it possible to determine the exact values of M and N from that? If so, say what they are. If not say why not.
Problem 4. This problem is about two-dimensional arrays (See Section 3.8.3 in the text). The declaration int A[100] [200] declares an array of 100 rows of 200 columns each. An array reference A[i][j] refers to the element in the ith row, jth column. Now, memory is actually linear, so there is a question as to how to compute the address of element A[i][j] The C specification guarantees that such arrays are laid out in row-major order, which means that the elements of row 0 (i.e., all the columns of row 0) come first, followed by the elements of row 1, etc. (Remember: "[Row][Column]") (See Figure 3.16 in the text, also slides 20, 22 and 24 from the lecture "Implementing Data Structures" on Friday 15 September.) a. For the array A declared above (100 rows of 200 columns each), with starting address 200000, what is the address of element A[47] [101]? b. Assume a global array declared as int *ptrs [10] [20]. The address of ptrs is in %rbx. Assume the value of int variables r and c are in registers %rdi and %rsi, respectively, and the last statement of a function that returns a pointer to an int is return ptrs [r] [c]; Write assembly code to put the return value in %rax c. Suppose a two-dimensional array is declared: char foo[M] {N]; where M and N are constants defined elsewhere. If you know that foo[r] [c] (for some values of r and c) is the same as *(foo+120), is it possible to determine the exact values of M and N from that? If so, say what they are. If not say why not.
Database System Concepts
7th Edition
ISBN:9780078022159
Author:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan
Publisher:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan
Chapter1: Introduction
Section: Chapter Questions
Problem 1PE
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![Problem 4. This problem is about two-dimensional arrays (See Section 3.8.3 in the text). The
declaration int A[100] [200] declares an array of 100 rows of 200 columns each. An array reference
A[i][j] refers to the element in the ith row, jth column. Now, memory is actually linear, so there
is a question as to how to compute the address of element A[i][j]
The C specification guarantees that such arrays are laid out in row-major order, which means
that the elements of row 0 (i.e., all the columns of row 0) come first, followed by the elements of row
1, etc. (Remember: "[Row][Column]") (See Figure 3.16 in the text, also slides 20, 22 and 24 from
the lecture "Implementing Data Structures" on Friday 15 September.)
a. For the array A declared above (100 rows of 200 columns each), with starting address 200000,
what is the address of element A[47] [101]?
b. Assume a global array declared as int *ptrs [10] [20]. The address of ptrs is in %rbx.
Assume the value of int variables r and c are in registers %rdi and %rsi, respectively, and
the last statement of a function that returns a pointer to an int is
return ptrs [r] [c];
Write assembly code to put the return value in %rax
c. Suppose a two-dimensional array is declared: char foo [M] {N]; where M and N are constants
defined elsewhere. If you know that foo[r] [c] (for some values of r and c) is the same as
*(foo+120), is it possible to determine the exact values of M and N from that? If so, say what
they are. If not say why not.](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2F2b2b0246-74c5-427f-bbae-6a253749f017%2F486ae203-29dd-49f8-b2bb-1a223d9c2906%2Fhijt8a_processed.png&w=3840&q=75)
Transcribed Image Text:Problem 4. This problem is about two-dimensional arrays (See Section 3.8.3 in the text). The
declaration int A[100] [200] declares an array of 100 rows of 200 columns each. An array reference
A[i][j] refers to the element in the ith row, jth column. Now, memory is actually linear, so there
is a question as to how to compute the address of element A[i][j]
The C specification guarantees that such arrays are laid out in row-major order, which means
that the elements of row 0 (i.e., all the columns of row 0) come first, followed by the elements of row
1, etc. (Remember: "[Row][Column]") (See Figure 3.16 in the text, also slides 20, 22 and 24 from
the lecture "Implementing Data Structures" on Friday 15 September.)
a. For the array A declared above (100 rows of 200 columns each), with starting address 200000,
what is the address of element A[47] [101]?
b. Assume a global array declared as int *ptrs [10] [20]. The address of ptrs is in %rbx.
Assume the value of int variables r and c are in registers %rdi and %rsi, respectively, and
the last statement of a function that returns a pointer to an int is
return ptrs [r] [c];
Write assembly code to put the return value in %rax
c. Suppose a two-dimensional array is declared: char foo [M] {N]; where M and N are constants
defined elsewhere. If you know that foo[r] [c] (for some values of r and c) is the same as
*(foo+120), is it possible to determine the exact values of M and N from that? If so, say what
they are. If not say why not.
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