With house number, you can locate a specific house number along a street as oppose to street name search which finds all occurrences of the street name. In long roads like Geylang Road or roads with offshoots of the same name, house numbering will take care of this problem but it has it's limitations.
In MapSource, putting the cursor over the road will show the address.
Testing of house numbering began in v3.64 (Aug 2007) on part of Geylang Rd and Telok Kurau area. Though the test data was left in subsequent versions, I did not intend implement it because it only worked on handheld GPS models then. Besides, it's a very tedious process, first I have to find out the actual addresses for each segment of road (from junction/node to junction/end node), then I have to specify which side of the road is odd and which is even numbered. Next, specify the start/end numbers on the left side and then the right side for each node. If it is a 4-way juction then this process has to be done 4 times. Multiply it by the thousands of junctions and end nodes in the map, that's the amount of painstaking work that has to be done.
There are some limitations in house numbering, it doesn't handle house number with alphabets like 12A, 12B, 12C, etc. House numbers are interpolated along the segment, that is, if the start of the segment is number 1 and the end is 15, number 7 will be in the middle. It doesn't consider that if there are numbers 1A to 1F (or due to different plot sizes), number 7 is actually two-thirds along the segment and not in the middle. So in some instances, it might not be exact but it should get you within 5-20m of the address.
Note: if you enter a house number that I have not covered yet, it will list all the occurences of the street name, ie if Bt Timah Road has 3 offshoots with the same name, it will be listed 4 times because it does not know on which street it is located.