Problem in MacBook Pro

Question

After copy some photos from a flash memory to my MacBook Pro, day by day my Mac is getting slow and slower. i have deleted the photos but problem still exist. now some of applications do not open, some Apps open but immediately exit with error, some Apps work slow.
please help me what is the problem and what shall i do?

Answer 1

Back up all data immediately as your boot drive may be failing.
If you have more than one user account, these instructions must be carried out as an administrator.
Triple-click anywhere in the line below to select it:
syslog -k Sender kernel -k Message CSeq "I/O error" | tail | open -f -a TextEdit
Copy the selected text to the Clipboard (command-C).
Launch the Terminal application in any of the following ways:
☞ Enter the first few letters of its name into a Spotlight search. Select it in the results (it should be at the top.)
☞ In the Finder, select Go ▹ Utilities from the menu bar, or press the key combination shift-command-U. The application is in the folder that opens.
☞ Open LaunchPad. Click Utilities, then Terminal in the icon grid.
Paste into the Terminal window (command-V).
The command may take a noticeable amount of time to run. Wait for a new line ending in a dollar sign (“$”) to appear.
A TextEdit window will open with the output of the command.
Normally the window will be empty. If you get output like this:
kernel[0] <Debug>: disk0s2: I/O error
the boot drive is failing, or there's some other hardware fault in the storage subsystem.