crashes on launch

on clicking play, i get crash report

Minecraft Crash Report ----
// Why did you do that?

Time: 14/08/15 18:15
Description: Initializing game

java.lang.OutOfMemoryError: Java heap space
at bmi.a(SourceFile:230)
at bmh.b(SourceFile:130)
at bmh.a(SourceFile:77)
at bot.j(SourceFile:553)
at bot.a(SourceFile:139)
at bou.a(SourceFile:23)
at bnn.a(SourceFile:99)
at ave.am(SourceFile:448)
at ave.a(SourceFile:310)
at net.minecraft.client.main.Main.main(SourceFile:124)

A detailed walkthrough of the error, its code path and all known details is as follows:
---------------------------------------------------------------------------------------

– Head –
Stacktrace:
at bmi.a(SourceFile:230)
at bmh.b(SourceFile:130)
at bmh.a(SourceFile:77)
at bot.j(SourceFile:553)
at bot.a(SourceFile:139)
at bou.a(SourceFile:23)
at bnn.a(SourceFile:99)
at ave.am(SourceFile:448)

– Initialization –
Details:
Stacktrace:
at ave.a(SourceFile:310)
at net.minecraft.client.main.Main.main(SourceFile:124)

– System Details –
Details:
Minecraft Version: 1.8.8
Operating System: Windows 7 (amd64) version 6.1
Java Version: 1.8.0_25, Oracle Corporation
Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
Memory: 3833336 bytes (3 MB) / 1060372480 bytes (1011 MB) up to 1060372480 bytes (1011 MB)
JVM Flags: 6 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx1G -XX:+UseConcMarkSweepGC -XX:+CMSIncrementalMode -XX:-UseAdaptiveSizePolicy -Xmn128M
IntCache: cache: 0, tcache: 0, allocated: 0, tallocated: 0
Launched Version: 1.8.8
LWJGL: 2.9.4
OpenGL: Mobile Intel(R) 4 Series Express Chipset Family GL version 2.1.0 - Build 8.15.10.1883, Intel
GL Caps: Using GL 1.3 multitexturing.
Using GL 1.3 texture combiners.
Using framebuffer objects because EXT_framebuffer_object is supported.
Shaders are available because OpenGL 2.1 is supported.
VBOs are available because OpenGL 1.5 is supported.

Using VBOs: No
Is Modded: Probably not. Jar signature remains and client brand is untouched.
Type: Client (map_client.txt)
Resource Packs: PureBDcraft 512x MC18.zip
Current Language: English (UK)
Profiler Position: N/A (disabled)
CPU: 2x Pentium(R) Dual-Core CPU T4300 @ 2.10GHz