Does your computer have integrated graphics? As in it uses some of the 4Gb RAM to drive the screen? 4Gb of RAM is too low for comfortable use, but it should still work, albeit some features might not work. How much memory is available to Photoshop in Preferences > Performance, and are you able to check 'Use Graphics Processor'?
It is using 2170 MB RAM and Yes i am able to use Check 'Use Graphic Processor' . It is showing Intel Graphic.