ITPEC FE Subject A October 2025 Question 14
In indirect addressing of direct file organization, which of the following is an appropriate method for calculating the record address from a record key in the superposition addressing method, or folding and adding method? Here, the record key is 123456 in decimal. The total number of records is 1,000, and the closest prime number to 1,000 is 997. The decimal number 123456 is equivalent to 361100 in octal.
Explanation
Split 123456 into 123 and 456 and add them, giving 579 — folding cuts the key into parts and sums them to form the address.
Direct file organisation computes a record's address from its key. The options are the standard address calculation methods:
- •Folding (superposition): split the key into equal-length parts and add them, 123 + 456 = 579
- •Division-remainder: divide by a prime close to the number of records and keep the remainder, 123456 − 123 × 997 = 825
- •Radix conversion: read the key in another base, octal 361100
- •Direct addressing: the key itself is the address, with no calculation
Answer (c)
Why not others:
- •(b) — is the division-remainder method
- •(a) — is the radix conversion method
- •(d) — is direct addressing; the question asks for indirect addressing, where the address is calculated from the key
Key rule: Each address calculation method has a signature operation: folding adds pieces of the key, division keeps a remainder by a prime, radix conversion changes the base.
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