When i turn on my sgh-a877 the screen is black but it make the sound when it is turned on how can i fix the screen

To unlock your samsung mobiles with codes are the best one, because it is easy & safe also,
Follow the instructions :

Warning : Do not enter any wrong unlock codes on your Samsung SGH-A877 Impression mobile phones. If you enter over a certain amount of wrong unlock codes on your Samsung SGH-A877 Impression mobile phone, your phone may get hard locked and sometimes become unusable.
Method 1:

1 - Switch ON your Samsung SGH-A877 Impression with a NOT ACCEPTED SIM Card.
2 - Samsung SGH-A877 Impression will ask for "Password".
3 - Enter the Unlock Code.

OR (if the Samsung SGH-A877 Impression shows "Insert Correct SIM Card")

Method 2:

1 - Switch ON your Samsung SGH-A877 Impression with a NOT ACCEPTED SIM Card.
2 - Don't bother about what's being displayed on your Samsung SGH-A877 Impression.
3 - Compose : #0111*CODE#.

NOT ACCEPTED: We mean, to use a sim card from a network other than the network your Samsung SGH-A877 Impression is locked to.
CODE: Its the unique Unlock Code for your Samsung SGH-A877 Impression.

If method 2 does not work, you can try method 2 again but this time without any SIM card on your Samsung SGH-A877 Impression.

Get the unlock code from this site http://www.theunlockspot.com/samsung-sgh-a877-impression/rs10wp9/ to your samsung mobile........

try hard reset

I think you tried to reboot it and than restore it. If that does not work you may need a trip to the Apple store or call Apple tech support.
The second way:ADDIN TIMER software installation, set up at 2 am, 4:00, 6:00, 8:00 and 1:00 automatic reboot.

Further reading :The solution for Samsung impression screen turned black

If you cannot get the screen to come back, by turning the phone off/on or by pulling the battery and putting it back in and restarting it, you will have to bring it to the tech at phone store you do business with. They may be able to fix it but may suggest a new phone. You can try giving it a light tap or moving around the slide keyboard where the wires come through to the screen. It could be a bad connection in the phone or a bad screen.

Sounds like your phone has a digitizer if the touch screen is not responding.you can purchase a digitizer on ebay, they cost anywhere from $9-16 and if you are in the U.S you can send it to us to fix it for you for a reasonable price.
http://shop.ebay.com/i.html?_nkw=+Samsung+SGH-A877+digitizer&_sacat=0&_odkw=C113+unlock+code&_osacat=0&_trksid=p3286.c0.m270.l1313

This is a device issue. You will need to contact your service provider for replacement options!

try taking the battery out while phone is turned on if that doesnt fix it you will need to replace the phone

your phone has either a flex problem or yoour screen may be damaged depending on how it happened.if your phone has flex problem phones likes samsung SGH-A877 has the capability to easily get spoit.so it just and advice when getting a phone,do not usually get flex phones they easily get spoit.But for this you could take it to an engineer to check exactly which is the problem if flex or screen.

it isn't activated

Hi! Most probable the software is broken, so you need to go to a specialized service and get it resofted.