1,000 kbytes is the value you get if you treat all six fields as 1-byte code and simply add up the character counts. 10 ＋ 10 ＋ 20 ＋ 40 ＋ 10 ＋ 10 ＝ 100 characters counted as 100 bytes gives 100 × 10,000 ＝ 1,000,000 bytes ＝ 1,000 kbytes. However, the department name, location, name, and job title use 2-byte code, so the character count must not be used directly as the byte count.
×Incorrectイ
1,500 kbytes is the value obtained if one record is estimated at 150 bytes, but adding up the six fields in the figure correctly always gives 180 bytes; there is no calculation path that yields 150 bytes. If you check the breakdown of 20 bytes for the 1-byte fields plus 160 bytes for the 2-byte fields, this value cannot be chosen.
○ウ
正解First add up the number of bytes for one record (one row) field by field, then multiply by the number of records. The business partner code and the phone number are each 10 characters in JIS 1-byte code, so 10 characters × 1 byte × 2 fields ＝ 20 bytes. The department name is 20 characters in 2-byte code, so 20 × 2 ＝ 40 bytes. The location is 40 characters in 2-byte code, so 40 × 2 ＝ 80 bytes. The name and the job title are each 10 characters in 2-byte code, so 10 × 2 × 2 fields ＝ 40 bytes. One record is therefore 20 ＋ 40 ＋ 80 ＋ 40 ＝ 180 bytes. For 10,000 records this gives 180 × 10,000 ＝ 1,800,000 bytes. Because the choices are lined up as 1,000／1,500／1,800／2,000, the question assumes the decimal conversion of 1 kbyte ＝ 1,000 bytes (dividing by 1,024 would give about 1,758 k, which is not among the choices). Hence 1,800,000 ÷ 1,000 ＝ 1,800 kbytes, so “ウ” is correct.
×Incorrectエ
2,000 kbytes is the opposite mistake: the value obtained when all six fields are counted as 2-byte code. A total of 100 characters × 2 bytes ＝ 200 bytes, and 200 × 10,000 ＝ 2,000,000 bytes ＝ 2,000 kbytes. The business partner code and the phone number use 1-byte code, so counting these two fields at 2 bytes overestimates the record by 20 bytes.
ここがポイント
Estimating a data volume is calculated as “bytes per record × number of records”. The bytes per record are obtained by computing (character count × bytes per character) for each field and adding them up.
JIS 1-byte code is counted as 1 byte per character, and 2-byte code as 2 bytes per character. The key point is not to confuse character count with byte count. For the conversion to kbytes, judge from the way the choices are lined up that it is the decimal conversion of 1 k ＝ 1,000 bytes.