Question 1

How do I convert octal to decimal manually?

Accepted Answer

Multiply each octal digit by 8 raised to its position power, then sum the results. For example, octal 37 = (3×8¹) + (7×8⁰) = 24 + 7 = 31 in decimal. For octal 377 = (3×64) + (7×8) + (7×1) = 192 + 56 + 7 = 255.

Question 2

What digits does the octal system use?

Accepted Answer

Octal uses exactly 8 digits: 0, 1, 2, 3, 4, 5, 6, and 7. The digits 8 and 9 do not exist in octal. Each position represents a power of 8, so from right to left: 8⁰=1, 8¹=8, 8²=64, 8³=512, and so on.

Question 3

What is octal 17 in decimal?

Accepted Answer

Octal 17 equals (1×8) + (7×1) = 8 + 7 = 15 in decimal. This can be confusing since '17' in octal looks like seventeen in decimal but actually represents fifteen. This is why specifying the base (e.g., 17₈ or 017 or 0o17) is important when writing octal numbers.

Question 4

How do Unix file permissions use octal?

Accepted Answer

Unix permissions are three groups of 3 bits: read (4), write (2), execute (1). Each group is summed: 7 = rwx (4+2+1), 6 = rw- (4+2), 5 = r-x (4+1), 4 = r-- (4). So a permission of 754 means owner=rwx (7), group=r-x (5), others=r-- (4). The octal-to-decimal converter helps verify these values.

Octal to Decimal Converter

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