Long description

The figure consists of seven vertical blocks labeled a, b, c, d, e, f and g which are given on time axis.

Block "a": The block is divided into three segments with increasing size from the bottom. The bottom segment is labeled operating system and the middle segment is labeled "A". The top segment is the largest and is shaded.

Block b: The block is divided into four segments and labeled from top to bottom as follows: Blank, B, A, Operating system. The top segment is shaded.

Block c: The block is divided into five segments and labeled from top to bottom as follows: Blank, C, B, A, Operating system. The top segment is shaded.

Block d: The block is divided into five segments and labeled from top to bottom as follows: Blank, C, B, blank, Operating system. The first and fourth segments are shaded.

Block e: The block is divided into five segments and labeled from top to bottom as follows: Blank, C, blank, D, Operating system. The first and third segments are shaded.

Block f: The block is divided into five segments and labeled from top to bottom as follows: Blank, C, A, D, Operating system. The top segment is shaded.